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Search: id:A097656
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| 2, 4, 9, 24, 81, 358, 2021, 13828, 109857, 986922, 9865125, 108507160, 1302065441, 16926805678, 236975181189, 3554627504844, 56874039618753, 966858672535762, 17403456103546565, 330665665962928288, 6613313319249128577
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OFFSET
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0,1
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FORMULA
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a(n) = Sum_{k=0..n) n!(k!+1) / k!(n-k)! = Sum_{k=0..n} (P(n, k) + C(n, k)) = Sum_{k=0..n} P(n, k) + 2^n = A007526(n) + A000079(n). - Ross La Haye (rlahaye(AT)new.rr.com), Aug 24 2006
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EXAMPLE
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a(2) = 9 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 = 9.
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MATHEMATICA
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f[n_] := Sum[n!(k! + 1)/(k!(n - k)!), {k, 0, n}]; Table[ f[n], {n, 0, 20}] (from Robert G. Wilson v Sep 24 2004)
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CROSSREFS
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Cf. A038507, A097204.
Sequence in context: A137154 A098448 A006406 this_sequence A012936 A013091 A013168
Adjacent sequences: A097653 A097654 A097655 this_sequence A097657 A097658 A097659
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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 20 2004
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