A152961 Base-2 logarithm of A136007(n)+1.

2, 3, 5, 7, 13, 17, 19, 31, 61, 127, 521, 2281, 3217, 4253, 9941, 19937, 21701, 23209, 44497, 110503, 216091, 859433, 1257787, 3021377, 6972593, 13466917, 20996011, 30402457, 32582657, 42643801, 57885161

Offset: 1

Author

Omar E. Pol, Dec 16 2008, Dec 20 2008

Keywords

• nonn
• hard
• more

Comments

The first 10 terms coincide with A109799.

Crossrefs

Intersection of A000043 and A136002.

Cf. A000523, A109799, A136003, A136005, A136007.

Programs

Mathematica

q[n_] := n == 2 || Module[{d = Divisors[(n+1)/2]}, AllTrue[Range[3, Length[d]], d[[#]] >= 2 * d[[#-1]] &]]; Select[MersennePrimeExponent[Range[48]], q] (* Amiram Eldar, Oct 20 2024 *)

Formula

a(n) = A000523(A136007(n)+1). - Michel Marcus, Apr 14 2021

Extensions

a(12)-(a31) from Amiram Eldar, Oct 20 2024