A216045 Numbers k such that Sum_{j=1..k-1} (4j)!/5^j is an integer.

1, 6, 30, 145, 151, 592, 732, 3895, 87806, 292432

Offset: 1

Author

Vaclav Kotesovec, Aug 30 2012

Keywords

• nonn
• more

Comments

Next term is > 1500000.

Crossrefs

Cf. A215972, A216042, A216043, A216044.

Programs

Mathematica

seq={}; sum=0; fak=1; k=0; While[k<10000, sum+=fak; If[Denominator[sum]==1, AppendTo[seq,k+1]]; k++; fak*=4*k*(4*k-1)*(4*k-2)*(4*k-3)/5;]; seq