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 A254966 #8 May 17 2019 14:51:56
%S A254966 1,7,469,3367,226051,1622881,108956107,782225269,52516617517,
%T A254966 377030956771,25312900687081,181728138938347,12200765614555519,
%U A254966 87592585937326477,5880743713315073071,42219444693652423561,2834506269052250664697,20349684749754530829919
%N A254966 Heptagonal numbers (A000566) that are also centered hexagonal numbers (A003215).
%H A254966 Colin Barker, <a href="/A254966/b254966.txt">Table of n, a(n) for n = 1..746</a>
%H A254966 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,482,-482,-1,1).
%F A254966 a(n) = a(n-1)+482*a(n-2)-482*a(n-3)-a(n-4)+a(n-5).
%F A254966 G.f.: -x*(x^4+6*x^3-20*x^2+6*x+1) / ((x-1)*(x^2-22*x+1)*(x^2+22*x+1)).
%e A254966 469 is in the sequence because it is the 14th heptagonal number and the 13th centered hexagonal number.
%t A254966 LinearRecurrence[{1,482,-482,-1,1},{1,7,469,3367,226051},20] (* _Harvey P. Dale_, May 17 2019 *)
%o A254966 (PARI) Vec(-x*(x^4+6*x^3-20*x^2+6*x+1)/((x-1)*(x^2-22*x+1)*(x^2+22*x+1)) + O(x^100))
%Y A254966 Cf. A000566, A003215, A254964, A254965.
%K A254966 nonn,easy
%O A254966 1,2
%A A254966 _Colin Barker_, Feb 11 2015