This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A144937 #3 Mar 31 2012 14:40:18 %S A144937 2,4,32,368,6752,171648,5638656,227787008,10932927488,608031869952, %T A144937 38451260291072,2724757330591744,213848122843791360, %U A144937 18412354032091807744,1725472542353497456640,174827224579118545174528 %N A144937 Number of hyperforests with n labeled vertices when edges of size 1 are allowed (with no two equal edges), with at least one component of order 1. %D A144937 D. E. Knuth: The Art of Computer Programming, Volume 4, Generating All Combinations and Partitions Fascicle 3, Section 7.2.1.4. Generating all partitions. Page 38, Algorithm H. %F A144937 a(n) = A134956(n) - A144935(n). %e A144937 For n=2 we do not have an hypertree of order 2. The possibilities are one forest, two hyperforests composed by one loop plus one tree and one hyperforest composed by two loops. So a(2)=4. %Y A144937 Cf. A134956(hyperforests), A144935(hyperforests without components of order 1). %K A144937 nonn %O A144937 1,1 %A A144937 _Washington Bomfim_, Sep 25 2008