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 A277495 #15 Oct 24 2016 04:36:31
%S A277495 1,2,2,1,5,2,3,4,3,2,3,2,3,4,6,6,7,6,4,2,3,4,5,8,4,5,3,2,4,6,6,7,9,10,
%T A277495 8,8,9,6,4,4,5,6,3,6,5,6,7,12,5,2,4,4,5,6,5,4,6,8,10,6,6,7,3,4,2,2,3,
%U A277495 6,9,14,6,2,3
%N A277495 a(1) = 1; a(n) = n if a(n-1) = 1; otherwise, a(n) = digit sum (n written in base a(n-1)).
%e A277495 a(15-1) = 4; 15 in base 4 is 33; 3+3 = 6, so a(15) = 6.
%t A277495 $RecursionLimit=100
%t A277495 a[1]=1;
%t A277495 a[n_]:=If[a[n-1]!=1,Total[IntegerDigits[n,a[n-1]]],n]
%t A277495 Array[a,100]
%o A277495 (PARI) lista(nn) = {print1(a = 1, ", "); for (n=2, nn, if (a==1, a = n, a = vecsum(digits(n, a));); print1(a, ", "););} \\ _Michel Marcus_, Oct 21 2016
%K A277495 nonn,base
%O A277495 1,2
%A A277495 _Cody M. Haderlie_, Oct 17 2016