A371831 a(n) = numerator(Sum_{k=1..n} k^2/k!).
0, 1, 3, 9, 31, 43, 217, 3913, 9133, 73067, 1972819, 6576067, 24112247, 372017527, 1612075951, 157983443203, 7109254944151, 37916026368811, 644572448269793, 34806912206568841, 2422459091299663, 7775794614048301, 277759159408419360043, 2036900502328408640323, 46848711553553398727437
Offset: 0
Links
- Eric Weisstein's World of Mathematics, Incomplete Gamma Function.
- Wikipedia, Incomplete gamma function.
Programs
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Mathematica
a[n_]:=Numerator[(2(E*Gamma[n+1,1]-1)-n)/n!]; Array[a,25,0]
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PARI
a(n) = numerator(sum(k=1, n, k^2/k!)); \\ Michel Marcus, Apr 07 2024