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

1,1

Links

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

Formula

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

Prog

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

Crossrefs

Cf. A135972, A242017. Subsequence of A056608.

Sequence in context: A291767 A135087 A294505 * A084038 A346540 A326930

Adjacent sequences: A242013 A242014 A242015 * A242017 A242018 A242019

Keyword

nonn

Author

Felix Fröhlich, Aug 11 2014

Status

approved