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 A254896 #7 Feb 04 2017 20:33:48
%S A254896 1,481,8321,4617761,79897441,44339739841,767175219361,425750177334721,
%T A254896 7366416376406081,4088053158428250401,70732329279075969601,
%U A254896 39253486001477883014881,679171818371271083701921,376911968498137474280636161,6521407729268615666629875041
%N A254896 Octagonal numbers (A000567) that are also centered square numbers (A001844).
%H A254896 Colin Barker, <a href="/A254896/b254896.txt">Table of n, a(n) for n = 1..503</a>
%H A254896 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,9602,-9602,-1,1).
%F A254896 a(n) = a(n-1)+9602*a(n-2)-9602*a(n-3)-a(n-4)+a(n-5).
%F A254896 G.f.: -x*(x^4+480*x^3-1762*x^2+480*x+1) / ((x-1)*(x^2-98*x+1)*(x^2+98*x+1)).
%e A254896 481 is in the sequence because it is the 13th octagonal number and the 16th centered square number.
%t A254896 LinearRecurrence[{1,9602,-9602,-1,1},{1,481,8321,4617761,79897441},30] (* _Harvey P. Dale_, Feb 04 2017 *)
%o A254896 (PARI) Vec(-x*(x^4+480*x^3-1762*x^2+480*x+1)/((x-1)*(x^2-98*x+1)*(x^2+98*x+1)) + O(x^100))
%Y A254896 Cf. A000567, A001844, A253673, A254895.
%K A254896 nonn,easy
%O A254896 1,2
%A A254896 _Colin Barker_, Feb 10 2015