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A368837
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a(n) = n! * (n+2)! * Sum_{k=0..n} 1/(k! * (k+2)!).
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2
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1, 4, 33, 496, 11905, 416676, 20000449, 1260028288, 100802263041, 9979424041060, 1197530884927201, 171246916544589744, 28769481979491076993, 5610048986000760013636, 1256650972864170243054465, 320445998080363411978888576
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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*(n+2)*a(n-1) + 1.
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PROG
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(PARI) a(n) = n!*(n+2)!*sum(k=0, n, 1/(k!*(k+2)!));
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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