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 A135208 #13 Jan 10 2024 16:37:23
%S A135208 1,1,2,3,4,5,6,7,8,9,1,2,12,16,12,14,21,14,27,29,29,24,21,16,18,29,29,
%T A135208 36,30,18,21,22,23,24,25,26,18,22,24,24,33,42,37,46,50,27,23,33,21,19,
%U A135208 37,48,52,26,36,33,36,60,36,42,28,42,37,36,43,42,51,60,33,46,49,64,45
%N A135208 a(n) = Sum_digits{C(n,Sum_digits[a(n-1)])}, with a(0)=1.
%H A135208 G. C. Greubel, <a href="/A135208/b135208.txt">Table of n, a(n) for n = 0..1000</a>
%p A135208 P:=proc(n) local a,i,k,w; a:=1; print(a); for i from 1 by 1 to n do w:=0; k:=a; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; k:=binomial(i,w); w:=0; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; a:=w; print(w); od; end: P(100);
%t A135208 nxt[{n_,a_}]:={n+1,Total[IntegerDigits[Binomial[n+1,Total[ IntegerDigits[ a]]]]]}; Transpose[NestList[nxt,{0,1},75]][[2]] (* _Harvey P. Dale_, Apr 24 2013 *)
%Y A135208 Cf. A128936, A129630, A129631, A130843.
%K A135208 base,easy,nonn
%O A135208 0,3
%A A135208 _Paolo P. Lava_, Dec 03 2007