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 A253546 #11 Aug 03 2021 20:28:01
%S A253546 1,547,368551,248402701,167423051797,112842888508351,
%T A253546 76055939431576651,51261590333994154297,34550235829172628419401,
%U A253546 23286807687272017560521851,15695273830985510663163308047,10578591275276546914954509101701,7129954824262561635168675971238301
%N A253546 Centered hexagonal numbers (A003215) which are also centered heptagonal numbers (A069099).
%H A253546 Colin Barker, <a href="/A253546/b253546.txt">Table of n, a(n) for n = 1..354</a>
%H A253546 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (675,-675,1).
%F A253546 a(n) = 675*a(n-1)-675*a(n-2)+a(n-3).
%F A253546 G.f.: -x*(x^2-128*x+1) / ((x-1)*(x^2-674*x+1)).
%e A253546 547 is in the sequence because it is the 14th centered hexagonal number and the 13th centered heptagonal number.
%t A253546 LinearRecurrence[{675,-675,1},{1,547,368551},20] (* _Harvey P. Dale_, Aug 03 2021 *)
%o A253546 (PARI) Vec(-x*(x^2-128*x+1) / ((x-1)*(x^2-674*x+1)) + O(x^100))
%Y A253546 Cf. A003215, A069099, A253457, A253458.
%K A253546 nonn,easy
%O A253546 1,2
%A A253546 _Colin Barker_, Jan 03 2015