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 A253622 #12 Mar 07 2016 12:57:20
%S A253622 1,106,15016,2132131,302747551,42988020076,6103996103206,
%T A253622 866724458635141,123068769130086781,17474898492013687726,
%U A253622 2481312517096813570276,352328902529255513291431,50028222846637186073812891,7103655315319951166968139056
%N A253622 Centered heptagonal numbers (A069099) which are also centered pentagonal numbers (A005891).
%H A253622 Colin Barker, <a href="/A253622/b253622.txt">Table of n, a(n) for n = 1..465</a>
%H A253622 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (143,-143,1).
%F A253622 a(n) = 143*a(n-1)-143*a(n-2)+a(n-3).
%F A253622 G.f.: -x*(x^2-37*x+1) / ((x-1)*(x^2-142*x+1)).
%F A253622 a(n) = (4+(6+sqrt(35))*(71+12*sqrt(35))^(-n)-(-6+sqrt(35))*(71+12*sqrt(35))^n)/16. - _Colin Barker_, Mar 07 2016
%e A253622 106 is in the sequence because it is the 6th centered heptagonal number and the 7th centered pentagonal number.
%t A253622 LinearRecurrence[{143,-143,1},{1,106,15016},20] (* _Harvey P. Dale_, Feb 25 2016 *)
%o A253622 (PARI) Vec(-x*(x^2-37*x+1)/((x-1)*(x^2-142*x+1)) + O(x^100))
%Y A253622 Cf. A005891, A069099, A133272, A253621.
%K A253622 nonn,easy
%O A253622 1,2
%A A253622 _Colin Barker_, Jan 06 2015