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Search: id:A122486
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| A122486 |
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a(n) = Sum_{k=0..n} |Stirling1(n,k)|*Bell(k)^2. |
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+0
1
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| 1, 1, 5, 39, 425, 6053, 107735, 2321469, 59152987, 1750362419, 59286010621, 2271617296347, 97502863649141, 4649359584613201, 244550369307356039, 14101227268075911837, 886551391533830227267, 60482082002935189216499
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OFFSET
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0,3
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FORMULA
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a(n) = exp(-2)*Sum_{r,s>=0} [r*s]^n/(r!*s!), where [m]^n = m*(m+1)*...*(m+n-1) is the rising factorial.
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MAPLE
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with(combinat): seq(sum(abs(stirling1(n, k))*bell(k)^2, k=0..n), n=0..19); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 08 2006
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CROSSREFS
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Cf. A000110, A059849.
Adjacent sequences: A122483 A122484 A122485 this_sequence A122487 A122488 A122489
Sequence in context: A024216 A127189 A121354 this_sequence A118991 A029538 A015874
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KEYWORD
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easy,nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Sep 15 2006, Sep 19 2006
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 08 2006
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