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Search: id:A097204
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| 0, 0, 1, 8, 49, 294, 1893, 13572, 109345, 985898, 9863077, 108503064, 1302057249, 16926789294, 236975148421, 3554627439308, 56874039487681, 966858672273618, 17403456103022277, 330665665961879712, 6613313319247031425
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OFFSET
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0,4
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COMMENT
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a(n) = Sum[n!(k!-1) / k!(n-k)! {k=0...n}]
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FORMULA
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a(n) = Sum[P(n, k) - C(n, k) {k=0...n}]
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EXAMPLE
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a(2) = 1 because P(2,0) = 1, P(2,1) = 2, P(2,2) = 2 while C(2,0) = 1, C(2,1) = 2, C(2,2) = 1 and 1 - 1 + 2 - 2 + 2 - 1 = 1.
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MAPLE
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A033312 := proc(n) factorial(n)-1; end: A097204 := proc(n) add( binomial(n, k)*A033312(k), k=1..n) ; end: seq(A097204(n), n=0..30) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 05 2007
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CROSSREFS
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Cf. A033312.
Sequence in context: A089383 A028443 A001108 this_sequence A037539 A037483 A024106
Adjacent sequences: A097201 A097202 A097203 this_sequence A097205 A097206 A097207
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KEYWORD
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nonn
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AUTHOR
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Ross La Haye (rlahaye(AT)new.rr.com), Sep 16 2004
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 05 2007
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