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 A202784 #16 Oct 14 2024 14:59:12 %S A202784 1,1,1,1,2,1,1,3,4,1,1,4,9,14,1,1,5,16,87,140,1,1,6,25,340,5673,4322, %T A202784 1,1,7,36,1001,89520,2577513,434542,1,1,8,49,2442,790425,290838284, %U A202784 8459809773,144109562,1,1,9,64,5215,4756140,11991502235,12092687195284,207495141083975,165431317452,1 %N A202784 T(n,k) is the number of n X n 0..k arrays with row and column sums equal. %H A202784 Andrew Howroyd, <a href="/A202784/b202784.txt">Table of n, a(n) for n = 0..119</a> (first 15 antidiagonals; terms up to n=61 from R. H. Hardin) %e A202784 Table starts %e A202784 n\k | 0 1 2 3 4 %e A202784 ----+------------------------------------------------------------------- %e A202784 0 | 1 1 1 1 1 ... %e A202784 1 | 1 2 3 4 5 ... %e A202784 2 | 1 4 9 16 25 ... %e A202784 3 | 1 14 87 340 1001 ... %e A202784 4 | 1 140 5673 89520 790425 ... %e A202784 5 | 1 4322 2577513 290838284 11991502235 ... %e A202784 6 | 1 434542 8459809773 12092687195284 3632894572698505 ... %e A202784 7 | 1 144109562 207495141083975 ... %e A202784 8 | 1 165431317452 ... %e A202784 ... %e A202784 Some solutions for n=4 k=3 %e A202784 ..3..1..2..1....2..2..0..3....1..1..1..2....1..3..0..0....1..2..0..2 %e A202784 ..2..3..2..0....1..2..2..2....3..0..1..1....1..0..1..2....3..1..0..1 %e A202784 ..2..2..0..3....3..0..3..1....0..3..2..0....2..0..1..1....0..0..3..2 %e A202784 ..0..1..3..3....1..3..2..1....1..1..1..2....0..1..2..1....1..2..2..0 %Y A202784 Rows n=0..5 are A000012, A000027(k+1), A000290(k+1), A202785, A202786, A202787. %Y A202784 Columns k=1..15 are A067209, A067210, A067211, A067212, A067213, A067214, A067215, A067216, A067217, A067218, A067219, A067220, A067221, A067222, A067223. %Y A202784 Cf. A008300, A257493. %K A202784 nonn,tabl %O A202784 0,5 %A A202784 _R. H. Hardin_, Dec 24 2011 %E A202784 Added crossrefs. - _R. H. Hardin_, Jan 05 2012 %E A202784 Row and column zero inserted by _Andrew Howroyd_, Oct 14 2024