A242016 Smallest prime factor of A135972(n), the n-th composite Mersenne number.

3, 3, 3, 7, 3, 23, 3, 3, 7, 3, 3, 3, 7, 3, 47, 3, 31, 3, 7, 3, 233, 3, 3, 7, 3, 31, 3, 223, 3, 7, 3, 13367, 3, 431, 3, 7, 3, 2351, 3, 127, 3, 7, 3, 6361, 3, 23, 3, 7, 3, 179951, 3, 3, 7, 3, 31, 3, 193707721, 3, 7, 3

Offset: 1

Author

Felix Fröhlich, Aug 11 2014

Keywords

• nonn

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..1201

Crossrefs

Cf. A135972, A242017. Subsequence of A056608.

Programs

PARI

for(n=2, 1e2, if(!ispseudoprime(2^n-1), p=factor(2^n-1)[1, 1]; print1(p, ", ")))

Formula

a(n) = A020639(A135972(n)).