A135977 Mersenne composites (A065341) with exactly 3 prime factors.

536870911, 8796093022207, 140737488355327, 9007199254740991, 2361183241434822606847, 9444732965739290427391, 604462909807314587353087

Offset: 1

Author

Artur Jasinski, Dec 09 2007

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..42

Crossrefs

Subsequence of A065341.

Cf. A000225, A054723, A134852, A135975, A135976, A135978, A135979, A344515.

Programs

Mathematica

k = {}; Do[If[ ! PrimeQ[2^Prime[n] - 1], c = FactorInteger[2^Prime[n] - 1]; d = Length[c]; If[d == 3, AppendTo[k, 2^Prime[n] - 1]]], {n, 1, 40}]; k

Formula

a(n) = 2^A344515(n) - 1. - Amiram Eldar, May 23 2021