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 A031298 #32 Mar 07 2023 11:55:23
%S A031298 0,1,2,3,4,5,6,7,8,9,0,1,1,1,2,1,3,1,4,1,5,1,6,1,7,1,8,1,9,1,0,2,1,2,
%T A031298 2,2,3,2,4,2,5,2,6,2,7,2,8,2,9,2,0,3,1,3,2,3,3,3,4,3,5,3,6,3,7,3,8,3,
%U A031298 9,3,0,4,1,4,2,4,3,4,4,4,5,4,6,4,7,4,8,4,9,4,0
%N A031298 Triangle T(n,k): write n in base 10, reverse order of digits.
%C A031298 The length of n-th row is given in A055642(n). - _Reinhard Zumkeller_, Jul 04 2012
%C A031298 According to the formula for T(n,1), columns are numbered starting with 1. One might also number columns starting with the offset 0, as to have the coefficient of 10^k in column k. - _M. F. Hasler_, Jul 21 2013
%H A031298 Reinhard Zumkeller, <a href="/A031298/b031298.txt">Rows n = 0..2500 of triangle, flattened</a>
%F A031298 T(n,1) = A010879(n); T(n,A055642(n)) = A000030(n). - _Reinhard Zumkeller_, Jul 04 2012
%t A031298 Table[Reverse[IntegerDigits[n]],{n,0,50}]//Flatten (* _Harvey P. Dale_, Mar 07 2023 *)
%o A031298 (Haskell)
%o A031298 a031298 n k = a031298_tabf !! n !! k
%o A031298 a031298_row n = a031298_tabf !! n
%o A031298 a031298_tabf = iterate succ [0] where
%o A031298 succ [] = [1]
%o A031298 succ (9:ds) = 0 : succ ds
%o A031298 succ (d:ds) = (d + 1) : ds
%o A031298 -- _Reinhard Zumkeller_, Jul 04 2012
%o A031298 (PARI) T(n,k)=n\10^(k-1)%10 \\ _M. F. Hasler_, Jul 21 2013
%Y A031298 Cf. A030308, A030341, A030386, A031235, A030567, A031007, A031045, A031087 for the base-2 to base-9 analogs.
%K A031298 nonn,base,tabf,less,look
%O A031298 0,3
%A A031298 _Clark Kimberling_
%E A031298 Initial 0 and better name by _Philippe Deléham_, Oct 20 2011
%E A031298 Edited by _M. F. Hasler_, Jul 21 2013