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 A101030 Triangle read by rows: T(n,k) = number of functions from an n-element set into but not onto a k-element set. 1
 0, 0, 2, 0, 2, 21, 0, 2, 45, 232, 0, 2, 93, 784, 3005, 0, 2, 189, 2536, 13825, 45936, 0, 2, 381, 7984, 61325, 264816, 818503, 0, 2, 765, 24712, 264625, 1488096, 5623681, 16736896, 0, 2, 1533, 75664, 1119005, 8172576, 38025127, 132766208, 387057609, 0 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS D. P. Walsh, A note on non-surjective functions from [n] to [k]. FORMULA T(n,k) =A089072(n,k)-A019538(n,k). T(n,k) = sum((-1)^(j-1)*C(k,j)*(k-j)^n, j=1..k). - Dennis P. Walsh, Apr 13 2016 T(n,k) = k^n - k!*Stirling2(n,k). - Dennis P. Walsh, Apr 13 2016 EXAMPLE T(3,3) = #(functions into) - #(functions onto) = 3^3 - 6 = 21 Triangle T(n,k) begins: 0, 0, 2, 0, 2, 21, 0, 2, 45, 232, 0, 2, 93, 784, 3005, 0, 2, 189, 2536, 13825, 45936, 0, 2, 381, 7984, 61325, 264816, 818503, 0, 2, 765, 24712, 264625, 1488096, 5623681, 16736896, 0, 2, 1533, 75664, 1119005, 8172576, 38025127, 132766208, 387057609 MAPLE T:=(n, k)->sum((-1)^(j-1)*binomial(k, j)*(k-j)^n, j=1..k); seq(seq(T(n, k), k=1..n), n=1..15); # Dennis P. Walsh, Apr 13 2016 CROSSREFS Cf. A199656, A036679 (diagonal). Sequence in context: A285152 A077184 A077183 * A093857 A056949 A281326 Adjacent sequences:  A101027 A101028 A101029 * A101031 A101032 A101033 KEYWORD nonn,tabl,easy AUTHOR Clark Kimberling, Nov 26 2004 EXTENSIONS Offset corrected from 0 to 1. Dennis P. Walsh, Apr 13 2016 STATUS approved

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Last modified June 15 16:13 EDT 2019. Contains 324142 sequences. (Running on oeis4.)