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 A216042 Numbers k such that Sum_{j=1..k-1} (2*j)!/4^j is an integer. 5
 1, 3, 53, 106, 427, 3416, 6806, 13665, 27330, 130030, 220227, 437666 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Next term > 1900000. LINKS Table of n, a(n) for n=1..12. MATHEMATICA seq={}; sum=0; fak=1; k=0; While[k<10000, sum+=fak; If[Denominator[sum]==1, AppendTo[seq, k+1]]; k++; fak*=k*(2k-1)/2; ]; seq CROSSREFS Cf. A215972, A216043, A216044, A216045. Sequence in context: A178608 A106997 A141929 * A292530 A036941 A215435 Adjacent sequences: A216039 A216040 A216041 * A216043 A216044 A216045 KEYWORD nonn,more AUTHOR Vaclav Kotesovec, Aug 30 2012 STATUS approved

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Last modified December 9 03:04 EST 2023. Contains 367681 sequences. (Running on oeis4.)