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Search: id:A129149
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| A129149 |
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Rencontres numbers: permutations with exactly 7 fixed points. |
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+0
1
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| 1, 0, 36, 240, 2970, 34848, 454740, 6362928, 95450355, 1527194240, 25962321528, 467321755680, 8879113408308, 177582268088640, 3729227629977720, 82043007859339296, 1886989180765048965, 45287740338360829056
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OFFSET
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0,3
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FORMULA
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G.f.: exp(-x)/(1-x)*(x^7/7!) . [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 03 2009]
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MAPLE
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a:=n->sum(n!*sum((-1)^k/(k-6)!, j=0..n), k=6..n): seq(a(n)/7!, n=6..24);
restart: G(x):=exp(-x)/(1-x)*(x^7/7!): f[0]:=G(x): for n from 1 to 26 do f[n]:=diff(f[n-1], x) od: x:=0: seq(f[n], n=7..24); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 03 2009]
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CROSSREFS
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Sequence in context: A112474 A166329 A159921 this_sequence A074363 A030165 A017342
Adjacent sequences: A129146 A129147 A129148 this_sequence A129150 A129151 A129152
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KEYWORD
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nonn
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AUTHOR
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Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 25 2007
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