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 A015515 #15 May 04 2023 08:57:17
%S A015515 1,1,14,2212,4171832,94375183504,25618521062894816,
%T A015515 83450744014073963641408,3262026661649164626974053098368,
%U A015515 1530121919008888925087797696409496422656,8612828743790947623482719127044813092555596516864
%N A015515 a(1) = 1, a(n) = Sum_{k=1..n-1} ((12^k - 1)/11)*a(k).
%H A015515 G. C. Greubel, <a href="/A015515/b015515.txt">Table of n, a(n) for n = 1..44</a>
%F A015515 a(n) = ((12^(n-1) + 10)/11) * a(n-1). - _Vincenzo Librandi_, Nov 12 2012
%t A015515 Join[{1},RecurrenceTable[{a[2]==1,a[n]==(12^(n-1)+10)/11 a[n-1]},a,{n,12}]] (* _Harvey P. Dale_, Mar 10 2013 *)
%o A015515 (Magma) [n le 2 select 1 else ((12^(n-1) + 10)/11) * Self(n-1): n in [1..15]]; // _Vincenzo Librandi_, Nov 12 2012
%o A015515 (SageMath)
%o A015515 def a(n, m) -> int: # a = A015515
%o A015515 return 1 if (n<3) else (m^(n-1)+m-2)*a(n-1, m)//(m-1)
%o A015515 [a(n, 12) for n in range(1,31)] # _G. C. Greubel_, May 03 2023
%Y A015515 Sequences with the recurrence a(n) = (m^(n-1) + m-2)*a(n-1)/(m-1): A036442 (m=2), A015502 (m=3), A015503 (m=4), A015506 (m=5), A015507 (m=6), A015508 (m=7), A015509 (m=8), A015511 (m=9), A015512 (m=10), A015513 (m=11), this sequence (m=12).
%K A015515 nonn,easy
%O A015515 1,3
%A A015515 _Olivier Gérard_