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 A033641 #6 Mar 30 2012 18:35:33 %S A033641 1,1,2,6,2,8,18,62,36,160,392,1496,1176,5664,14856,61560,5664,20520, %T A033641 102600,313464,123120,539184,1514952,5207160,3569088,15498360, %U A033641 43342056,164591976,145524528,682642512,1966450584,8092803816,1365285024 %N A033641 Base 4 digital convolution sequence. %e A033641 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. %K A033641 base,nonn %O A033641 0,3 %A A033641 _David W. Wilson_