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A166677
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a(n)= n*(a(n-1)+4), a(0)=1.
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1
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1, 5, 18, 66, 280, 1420, 8544, 59836, 478720, 4308516, 43085200, 473937244, 5687246976, 73934210740, 1035078950416, 15526184256300, 248418948100864, 4223122117714756, 76016198118865680, 1444307764258447996
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = n!*(1 + Sum_{k=0..n-1} 4/k!) = n! + 4 e n Gamma(n,1).
E.g.f.: (1+4*x*exp(x))/(1-x). (End)
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MAPLE
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f:= gfun:-rectoproc({a(n)=n*(a(n-1)+4), a(0)=1}, a(n), remember):
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MATHEMATICA
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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