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 A334689 Triangle read by rows: T(n,k) (0 <= k <= n) =  k!*(Stirling2(n,k)+(k+1)*Stirling2(n,k+1))^2. 1
 1, 1, 1, 1, 9, 2, 1, 49, 72, 6, 1, 225, 1250, 600, 24, 1, 961, 16200, 25350, 5400, 120, 1, 3969, 181202, 735000, 470400, 52920, 720, 1, 16129, 1866312, 17360406, 26460000, 8490720, 564480, 5040, 1, 65025, 18301250, 362237400, 1159593624, 840157920, 153679680, 6531840, 40320 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS This is the number of Boolean matrices of dimension n and rank k having a Moore-Penrose inverse (Kim-Roush, Th. 10). Theorem 8 of the same Kim-Roush paper gives a formula for the number of Boolean matrices of dimension n and rank k having a minimum-norm g-inverse. Unfortunately the formula appears to produce negative numbers. LINKS Ki Hang Kim, and Fred W. Roush, Inverses of Boolean matrices, Linear Algebra and its Applications 22 (1978): 247-262. See Th. 10. EXAMPLE Triangle begins: 1, 1, 1, 1, 9, 2, 1, 49, 72, 6, 1, 225, 1250, 600, 24, 1, 961, 16200, 25350, 5400, 120, 1, 3969, 181202, 735000, 470400, 52920, 720, 1, 16129, 1866312, 17360406, 26460000, 8490720, 564480, 5040, ... MAPLE T := (n, k) -> k!*(Stirling2(n, k)+(k+1)*Stirling2(n, k+1))^2; r:=n->[seq(T(n, k), k=0..n)]; for n from 0 to 12 do lprint(r(n)); od: CROSSREFS Columns k=0-2 give: A000012, A060867, 2*A129839(n+1). Row sums give A014235. Sequence in context: A010536 A239908 A293171 * A335086 A151898 A080994 Adjacent sequences:  A334686 A334687 A334688 * A334690 A334691 A334692 KEYWORD nonn,tabl AUTHOR N. J. A. Sloane, May 11 2020 STATUS approved

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Last modified December 4 21:14 EST 2020. Contains 338938 sequences. (Running on oeis4.)