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A047792
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a(n) = Sum_{k=0..n} Stirling1(n,k)*Stirling2(n,k).
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4
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1, 1, 0, -6, 36, 50, -6575, 145222, -1489978, -49083480, 4200404478, -182031111702, 4165517606173, 176264238017452, -33427749628678925, 2913726991238703330, -165770248921085801710, 1422295225609567363172, 1326793746164926878993976
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OFFSET
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0,4
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LINKS
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MAPLE
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seq(add(stirling1(n, k)*stirling2(n, k), k = 0..n), n = 0..20); # G. C. Greubel, Aug 07 2019
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MATHEMATICA
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Flatten[{1, Table[Sum[StirlingS1[n, k]*StirlingS2[n, k], {k, n}], {n, 20}] }] (* Vaclav Kotesovec, Oct 13 2018 *)
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PROG
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(PARI) {a(n) = sum(k=0, n, stirling(n, k, 1)*stirling(n, k, 2))};
(Magma) [(&+[StirlingFirst(n, k)*StirlingSecond(n, k): k in [0..n]]): n in [0..20]]; // G. C. Greubel, Aug 07 2019
(Sage) [sum((-1)^(n-k)*stirling_number1(n, k)*stirling_number2(n, k) for k in (0..n)) for n in (0..20)] # G. C. Greubel, Aug 07 2019
(GAP) List([0..20], n-> Sum([0..n], k-> (-1)^(n-k)*Stirling1(n, k) *Stirling2(n, k) )); # G. C. Greubel, Aug 07 2019
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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