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 A053874 #13 Jan 17 2022 04:00:58 %S A053874 1,2,1,1,2,2,2,1,1,2,2,3,4,3,2,2,1,1,2,2,3,5,7,9,11,12,11,9,7,5,3,2,2, %T A053874 1,1,2,2,3,5,8,14,23,35,55,84,117,158,204,242,274,290,274,242,204,158, %U A053874 117,84,55,35,23,14,8,5,3,2,2,1,1,2,2,3,5,8,15,29,54,107,227,495,1131 %N A053874 Triangle T(n,k) = number of Boolean functions mapping {0,1}^n to {0,1}^n with image of size k (k = 0...2^n) under action of GL(n,2). %H A053874 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a053/A053874.java">Java program</a> (github) %H A053874 <a href="/index/Bo#Boolean">Index entries for sequences related to Boolean functions</a> %e A053874 Triangle begins: %e A053874 1, 2, 1; %e A053874 1, 2, 2, 2, 1; %e A053874 1, 2, 2, 3, 4, 3, 2, 2, 1; %e A053874 ... %Y A053874 Row sums give A000585. %K A053874 nonn,tabf,nice %O A053874 1,2 %A A053874 _Vladeta Jovovic_, Mar 30 2000