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 A090636 #15 Nov 29 2019 20:48:23
%S A090636 15,8,12,16,32,80,176,368,752,1520,3424,8592,20096,70464,235072,
%T A090636 705280,3023616,13223680,55540736,278539264,1392697344,9541095424,
%U A090636 58609614848,410267320320,3397142953984,24143851798528,176071227916288,1232666139967488
%N A090636 Trajectory of 15 under the map k -> A003415(k) (taking the arithmetic derivative).
%F A090636 a(n) = A129150(n-2) for n>1. - _Reinhard Zumkeller_, Apr 01 2007
%o A090636 (Haskell)
%o A090636 a090636 n = a090636_list !! (n-1)
%o A090636 a090636_list = iterate a003415 15 -- _Reinhard Zumkeller_, Apr 29 2012
%o A090636 (PARI) A090636(n,a=15)={if(n<0, vector(-n,n, if(n>1, a=A003415(a), a)), for(n=2,n, a=A003415(a)); a)} \\ For n<0 return the vector a[1..-n]. - _M. F. Hasler_, Nov 27 2019
%K A090636 nonn
%O A090636 1,1
%A A090636 _N. J. A. Sloane_, Dec 14 2003
%E A090636 More explicit name from _M. F. Hasler_, Nov 27 2019