A292238 a(n) = gpf(lpf(2^prime(n) - 1) - 1) where prime(n) is the n-th prime.

2, 3, 5, 7, 11, 13, 257, 73, 23, 29, 331, 37, 163, 43, 47, 53, 61, 1321, 2677, 1609, 73, 79, 83, 2931542417, 97, 278557, 599, 28059810762433, 31981, 113, 77158673929, 131, 27977333, 457, 37888318897441, 151, 4523, 461, 541, 173, 179, 181, 191, 587, 197, 3690437

Offset

1,1

Links

Table of n, a(n) for n=1..46.

Formula

For p in A291691, let pp be such that p = prime(pp), then a(pp) = p.

Prog

(PARI) a(n) = vecmax(factor(vecmax(factor(2^prime(n)-1)[, 1])-1)[, 1]);

Crossrefs

Cf. A001348, A291691, A292237.

Sequence in context: A029979 A029981 A029982 * A289863 A260904 A245808

Adjacent sequences: A292235 A292236 A292237 * A292239 A292240 A292241

Keyword

nonn

Author

Michel Marcus, Sep 12 2017

Status

approved