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 A364068 #11 Jul 26 2023 06:11:21 %S A364068 0,1,0,2,1,0,9,9,1,0,44,216,44,1,0,265,7570,7570,265,1,0,1854,357435, %T A364068 1975560,357435,1854,1,0,14833,22040361,749649145,749649145,22040361, %U A364068 14833,1,0,133496,1721632024 %N A364068 Triangle T(n,k) read by rows: Number of traceless binary n X n matrices with all row and column sums equal to k, 1<=k<=n. %F A364068 T(n,n)=0. (k=n would require a 1 on the diagonal) %F A364068 T(n,n-1)=1. (1 at all entries but the diagonal) %F A364068 T(n,n-k) = T(n,k-1). (Flip entries 0<->1 and erase diagonal) - _R. J. Mathar_, Jul 26 2023 %e A364068 0 %e A364068 1 0 %e A364068 2 1 0 %e A364068 9 9 1 0 %e A364068 44 216 44 1 0 %e A364068 265 7570 7570 265 1 0 %e A364068 1854 357435 1975560 357435 1854 1 0 %e A364068 14833 22040361 749649145 %Y A364068 Cf. A000166 (k=1), A007107 (k=2), A284989 (see 1st col), A284990 (see 1st col, k=3), A007105 (k=3?), A284991 (see 1st col, k=4), A008300 (any trace) %K A364068 nonn,tabl,more %O A364068 1,4 %A A364068 _R. J. Mathar_, Jul 04 2023