{"title":"RECURRENCE RELATIONS","authors":"David Popović","doi":"10.1142/9789814355162_0006","DOIUrl":"https://doi.org/10.1142/9789814355162_0006","url":null,"abstract":"In order to help analyze this, you built the following table: Number People Sick total 1 2 3 4 number Day day days days days sick Comments 0 1 0 0 0 1 Poor Sucker 1 2 1 0 0 3 Spreads to Family 2 6 2 1 0 9 Uh Oh 3 18 6 2 1 27 Look out! 4 54 18 6 2 80 Original person dead! 5 160 54 18 6 238 Government begins cover-up 6 476 160 54 18 708 Back page of newspapers 7 1416 476 160 54 2106 Displaces war news","PeriodicalId":193527,"journal":{"name":"Enumerative Combinatorics","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115576736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"THE PRINCIPLE OF INCLUSION AND EXCLUSION","authors":"James Joseph Sylvester","doi":"10.1142/9789814401920_0013","DOIUrl":"https://doi.org/10.1142/9789814401920_0013","url":null,"abstract":"The Principle of Inclusion and Exclusion, hereafter called PIE, gives a formula for the size of the union of n finite sets. Usually the universe is finite too. It is a generalisation of the familiar formulas |A ∪ B| = |A| + |B| − |A ∩ B| and |A ∪ B ∪ C| = |A| + |B| + |C| − |A ∩ B| − |A ∩ C| − |B ∩ C| + |A ∩ B ∩ C|. That is, the cardinality of the union P 1 ∪ P 2 ∪. .. ∪ P k can be calculated by including (adding) the sizes of all of the sets together, then excluding (subtracting) the sizes of the intersections of all pairs of sets, then including the sizes of the intersections of all triples, excluding the sizes of the intersections of all quadruples, and so on until, finally, the size of the intersection of all of the sets has been included or excluded, as appropriate. If n is odd it is included, and if n is even it is excluded. The formula can be expressed more compactly as |P 1 ∪ P 2 ∪ · · · ∪ P n | = k i=1 (−1) k 1≤i 1 <i 2 <···<i k ≤n |P i 1 ∩ P i 2 ∩ · · · ∩ P i k |. It is important to remember that all sets involved must be finite. To prove PIE, both sides count only elements that belong to some positive number of the sets. Each of these is counted once on the LHS. To determine the number of times it is counted on the RHS, suppose it belongs to t ≥ 1 of the sets, and calculate the contribution it makes to each intersection. You'll end up making use of the Binomial Theorem expansion of (1 + (−1)) t. When to use PIE. Vaguely speaking, you should try PIE when you are trying to count something described by a bunch of conditions, any number of which might hold at the same time, and you can't see how to organise the counting by cases. Often PIE is used in conjunction with counting the complement. That is, you use it to count the number of objects in the universe that you don't want, and subtract this from the size of the universe (which needs to be finite!). In applying PIE, the …","PeriodicalId":193527,"journal":{"name":"Enumerative Combinatorics","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129238981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"STIRLING NUMBERS","authors":"Methodus Dlfferentialis","doi":"10.1201/9781315273112-14","DOIUrl":"https://doi.org/10.1201/9781315273112-14","url":null,"abstract":"This monograph is based on a set of notes taken from lectures on combinatorics given by Professor Gian-Carlo Rota at thl Massachusetss Institute of Te~hnology in 19690 It is indeed a pleasure to finally gather this material under one cover-not so much for the originality of the results as for the Originality of the methodology. Professor Rota's constructivist approach enabled me to formulate a general modus operand:!. which may, indeed, serve combina torics in a far broader sense' than is offered hereo It is all the more fitting that this material be issued through a Computer Science Department J as our methods of abs1l;Y'8ct reasoning are much more akin to those of the computer programmer than to the traditional \"Sa~~ Beweis\" style of classical mathemat'1cso Such methods may, hopefully one day extend beyond combinator-ics to other areas of mathematics","PeriodicalId":193527,"journal":{"name":"Enumerative Combinatorics","volume":"8 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122865907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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