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 A104612 #4 Nov 06 2022 17:30:44
%S A104612 1,3,6,1,3,6,2,2,2,7,4,5,1,0,1,0,1,1,2,1,1,5,1,1,0,2,2,3,2,2,7,3,3,3,
%T A104612 3,3,0,4,4,5,4,5,2,5,5,0,6,6,6,7,7,4,7,0,1,1,0,5,1,3,2,1,1,1,2,2,1,3,
%U A104612 5,3,1,1,4,7,3,5,0,6,1,1,7,4,7,1,3,0,2,2,1,1,5,7,6,3,2,2,4,6,4,0,1,6,2,2,0
%N A104612 Write the natural numbers in base 8 in a triangle with k digits in the k-th row, as shown below. Sequence gives the leading diagonal.
%C A104612 1
%C A104612 23
%C A104612 456
%C A104612 7101
%C A104612 11213
%C A104612 141516...
%t A104612 t = Flatten[ IntegerDigits[ Range[1750], 8]]; t[[Table[n(n + 1)/2, {n, 105}]]]
%t A104612 TakeList[Flatten[IntegerDigits[Range[3000],8]],Range[150]][[All,-1]] (* _Harvey P. Dale_, Nov 06 2022 *)
%Y A104612 Cf. A104606, A104607, A104608, A104609, A104610, A104611, A104613, A091425, A104614, A104615, A104616, A104617, A104618, A104619, A104620.
%K A104612 base,nonn
%O A104612 1,2
%A A104612 _Robert G. Wilson v_, Mar 16 2005