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 A033647 #8 Apr 14 2021 12:11:00 %S A033647 1,1,2,6,24,120,720,5040,40320,362880,40320,403200,846720,2943360, %T A033647 12620160,66044160,408885120,2928240000,23834805120,217441486080, %U A033647 47669610240,482552582400,1060444385280,4146438320640,18706642053120,101826086906880,648369805547520 %N A033647 Base 10 digital convolution sequence. %H A033647 Alois P. Heinz, <a href="/A033647/b033647.txt">Table of n, a(n) for n = 0..1000</a> %e A033647 Suppose base = 3 and a(0)..a(13) are 1 1 2 1 3 7 6 20 52 6 26 104 32 162. In base 3, 14 = 112, so we convolve the last three terms with 1, 1, 2 to obtain 104*1+32*1+162*2 = 460. %p A033647 a:= proc(n) option remember; `if`(n=0, 1, (l-> %p A033647 add(l[i]*a(n-i), i=1..nops(l)))(convert(n, base, 10))) %p A033647 end: %p A033647 seq(a(n), n=0..33); # _Alois P. Heinz_, Apr 14 2021 %Y A033647 Cf. A033639, A033640, A033641, A033642, A033643, A033644, A033645, A033646. %K A033647 base,nonn %O A033647 0,3 %A A033647 _David W. Wilson_