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 A229418 #5 Jul 23 2025 05:44:06 %S A229418 152,4743,59008,426425,2164680,8583967,28371968,81545697,209841400, %T A229418 493679879,1078445952,2213497273,4308069416,8009070975,14306664448, %U A229418 24674505857,41252568408,67081603015,106399491200,165011023737 %N A229418 Number of 4X4 0..n zero-diagonal arrays with corresponding row and column sums equal. %C A229418 Row 4 of A229417 %F A229418 Empirical: a(n) = (29/140)*n^9 + (261/140)*n^8 + (811/105)*n^7 + (289/15)*n^6 + (1921/60)*n^5 + (2221/60)*n^4 + (6323/210)*n^3 + (3539/210)*n^2 + (208/35)*n + 1 %e A229418 Some solutions for n=4 %e A229418 ..0..1..1..4....0..1..1..4....0..0..2..4....0..0..1..3....0..1..2..3 %e A229418 ..0..0..1..2....4..0..1..3....0..0..3..1....1..0..2..2....2..0..3..2 %e A229418 ..2..0..0..1....2..3..0..0....4..0..0..1....0..3..0..2....1..4..0..3 %e A229418 ..4..2..1..0....0..4..3..0....2..4..0..0....3..2..2..0....3..2..3..0 %K A229418 nonn %O A229418 1,1 %A A229418 _R. H. Hardin_ Sep 22 2013