cp's OEIS Frontend

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.

A002862 Number of nonisomorphic connected functions with no fixed points, or proper rings with n edges.

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%I A002862 M1403 N0547 #35 Oct 02 2017 02:14:09
%S A002862 0,1,2,5,11,31,77,214,576,1592,4375,12183,33864,94741,265461,746372,
%T A002862 2102692,5938630,16803610,47639902,135288198,384812502,1096141974,
%U A002862 3126648842,8929715592,25533447030,73090099586,209438176485,600721031344,1724585494225
%N A002862 Number of nonisomorphic connected functions with no fixed points, or proper rings with n edges.
%D A002862 R. A. Fisher, Contributions to Mathematical Statistics, Wiley, 1950, 41.399.
%D A002862 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A002862 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A002862 Alois P. Heinz, <a href="/A002862/b002862.txt">Table of n, a(n) for n = 1..750</a>
%H A002862 R. K. Guy, <a href="/A000081/a000081.pdf">Letter to N. J. A. Sloane, 1988-04-12</a> (annotated scanned copy) Includes illustrations for n <= 6.
%t A002862 Needs["Combinatorica`"]; nn=30;s[n_,k_]:=s[n,k]=a[n+1-k]+If[n<2 k,0,s[n-k,k]];a[1]=1;a[n_]:=a[n]=Sum[a[i] s[n-1,i] i,{i,1,n-1}]/(n-1);rt=Table[a[i],{i,1,nn}];cfd=Drop[Apply[Plus,Table[Take[CoefficientList[CycleIndex[CyclicGroup[n],s]/.Table[s[j]->Table[Sum[rt[[i]] x^(k*i),{i,1,nn}],{k,1,nn}][[j]],{j,1,nn}],x],nn],{n,2,30}]],1]  (* _Geoffrey Critzer_, Oct 14 2012, after code given by _Robert A. Russell_ in A000081 *)
%Y A002862 (A002861) minus (A000081).
%K A002862 nonn,nice
%O A002862 1,3
%A A002862 _N. J. A. Sloane_
%E A002862 More terms and better description from _Christian G. Bower_