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 A254333 #14 Jul 25 2024 21:44:15
%S A254333 1,16,1156,22801,1666681,32878756,2403352576,47411143081,
%T A254333 3465632747641,68366835443776,4997440018745476,98584929298781641,
%U A254333 7206305041398228481,142159399682007682276,10391486872256226723856,204993755756525779060081,14984516863488437537571601
%N A254333 Squares (A000290) which are also centered pentagonal numbers (A005891).
%H A254333 Colin Barker, <a href="/A254333/b254333.txt">Table of n, a(n) for n = 1..634</a>
%H A254333 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,1442,-1442,-1,1).
%F A254333 a(n) = a(n-1)+1442*a(n-2)-1442*a(n-3)-a(n-4)+a(n-5).
%F A254333 G.f.: -x*(x^4+15*x^3-302*x^2+15*x+1) / ((x-1)*(x^2-38*x+1)*(x^2+38*x+1)).
%e A254333 16 is in the sequence because it is the 4th square number and the 3rd centered pentagonal number.
%t A254333 LinearRecurrence[{1,1442,-1442,-1,1},{1,16,1156,22801,1666681},20] (* _Harvey P. Dale_, Jul 26 2015 *)
%o A254333 (PARI) Vec(-x*(x^4+15*x^3-302*x^2+15*x+1) / ((x-1)*(x^2-38*x+1)*(x^2+38*x+1)) + O(x^100))
%Y A254333 Cf. A000290, A005891, A129557, A254332.
%K A254333 nonn,easy
%O A254333 1,2
%A A254333 _Colin Barker_, Jan 28 2015