A216044 Numbers k such that Sum_{j=1..k-1} (4j)!/16^j is an integer.

1, 3, 13, 15, 61, 106, 253, 27545, 62785, 218107, 1004593

Offset

1,2

Comments

Next term > 1200000.

Links

Table of n, a(n) for n=1..11.

Mathematica

seq={}; sum=0; fak=1; k=0; While[k<10000, sum+=fak; If[Denominator[sum]==1, AppendTo[seq, k+1]]; k++; fak*=k*(4*k-1)*(4*k-2)*(4*k-3)/4; ]; seq

Crossrefs

Cf. A215972, A216042, A216043, A216045.

Sequence in context: A152270 A032919 A340018 * A023144 A152269 A063674

Adjacent sequences: A216041 A216042 A216043 * A216045 A216046 A216047

Keyword

nonn,more

Author

Vaclav Kotesovec, Aug 30 2012

Status

approved