login
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
OFFSET
1,2
COMMENTS
Next term > 1900000.
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
KEYWORD
nonn,more
AUTHOR
Vaclav Kotesovec, Aug 30 2012
STATUS
approved