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 A222821 #7 Jul 23 2025 03:05:53 %S A222821 2,2,8,2,12,50,2,16,122,452,2,20,218,2052,5682,2,24,344,5584,54182, %T A222821 96608,2,28,488,12476,248442,2236302,2185738,2,32,668,23568,855192, %U A222821 20394466,145121216,65108492,2,36,860,41668,2319872,126252320 %N A222821 T(n,k)=Number of idempotent n X n 0..k matrices. %C A222821 Table starts %C A222821 ........2.........2........2.........2.......2.....2...2..2.2 %C A222821 ........8........12.......16........20......24....28..32.36 %C A222821 .......50.......122......218.......344.....488...668.860 %C A222821 ......452......2052.....5584.....12476...23568.41668 %C A222821 .....5682.....54182...248442....855192.2319872 %C A222821 ....96608...2236302.20394466.126252320 %C A222821 ..2185738.145121216 %C A222821 .65108492 %e A222821 Some solutions for n=3 k=4 %e A222821 ..0..2..0....1..0..0....0..0..3....1..0..0....0..0..0....0..3..0....1..4..1 %e A222821 ..0..1..0....3..0..2....0..0..4....0..1..0....4..1..0....0..1..0....0..0..0 %e A222821 ..0..2..0....0..0..1....0..0..1....4..2..0....0..0..0....0..2..0....0..0..0 %K A222821 nonn,tabl %O A222821 1,1 %A A222821 _R. H. Hardin_ Apr 09 2013