A216043 Numbers k such that Sum_{j=1..k-1} (2j)!/3^j is an integer.

1, 4, 12, 105, 112, 322, 8807, 8831

Offset

1,2

Comments

Next term > 2000000.

Links

Table of n, a(n) for n=1..8.

Mathematica

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

Crossrefs

Cf. A215972, A216042, A216044, A216045

Sequence in context: A012278 A070040 A079822 * A245647 A080448 A155174

Adjacent sequences: A216040 A216041 A216042 * A216044 A216045 A216046

Keyword

nonn,more

Author

Vaclav Kotesovec, Aug 30 2012

Status

approved