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 A253579 #9 Jun 13 2015 00:55:21 %S A253579 1,22801,1666681,47411143081,3465632747641,98584929298781641, %T A253579 7206305041398228481,204993755756525779060081, %U A253579 14984516863488437537571601,426256225957302372068628976801,31158234954289838149958560780201,886340998518823181233611960679431001 %N A253579 Centered pentagonal numbers (A005891) which are also centered octagonal numbers (A016754). %H A253579 Colin Barker, <a href="/A253579/b253579.txt">Table of n, a(n) for n = 1..317</a> %H A253579 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2079362,-2079362,-1,1). %F A253579 a(n) = a(n-1)+2079362*a(n-2)-2079362*a(n-3)-a(n-4)+a(n-5). %F A253579 G.f.: -x*(x^4+22800*x^3-435482*x^2+22800*x+1) / ((x-1)*(x^2-1442*x+1)*(x^2+1442*x+1)). %e A253579 22801 is in the sequence because it is the 96th centered pentagonal number and the 76th centered octagonal number. %o A253579 (PARI) Vec(-x*(x^4+22800*x^3-435482*x^2+22800*x+1)/((x-1)*(x^2-1442*x+1)*(x^2+1442*x+1)) + O(x^100)) %Y A253579 Cf. A005891, A016754, A253410, A253411. %K A253579 nonn,easy %O A253579 1,2 %A A253579 _Colin Barker_, Jan 04 2015