A139295 -id:A139295 - cp's OEIS frontend

A139305 a(n) = (2^(2p - 1)/32)-1, where p is the n-th Mersenne prime A000668(n).

0, 255, 72057594037927935, 452312848583266388373324160190187140051835877600158453279131187530910662655

Offset: 1

Omar E. Pol, Apr 13 2008

nonn

Next term is too large to list here.

Cf. A000668, A139286, A139294, A139295, A139296, A139297, A139298, A139299, A139300, A139301, A139302, A139303, A139304, A139306.

a[n_] := 2^(2^(MersennePrimeExponent[n] + 1) - 8) - 1; Array[a, 4] (* Amiram Eldar, Jul 10 2025 *)

a(n) = (2^(2*A000668(n)-1)/32)-1 = (A139294(n)/32)-1.

Edited by Max Alekseyev, Apr 23 2010

A139307 a(n) = (2^(2*p - 1)) - 1, where p is A000043(n).

Original entry on oeis.org

7, 31, 511, 8191, 33554431, 8589934591, 137438953471, 2305843009213693951, 2658455991569831745807614120560689151, 191561942608236107294793378393788647952342390272950271

Offset: 1

Omar E. Pol, Apr 13 2008, May 08 2008

nonn

Ultraperfect numbers (A139306) minus 1.

			a(5) = 33554431 because A000043(5) = 13 and (2^(2*13 - 1))-1 = 2^25 - 1 = 33554431.

Amiram Eldar, Table of n, a(n) for n = 1..15

Cf. A000043, A139287, A139295, A139306.

2^(2 * MersennePrimeExponent[Range[10]] - 1) - 1 (* Amiram Eldar, Oct 17 2024 *)

a(n) = (2^(2*A000043(n) - 1)) - 1 = A139306(n) - 1.

cp's OEIS Frontend

A139305 a(n) = (2^(2p - 1)/32)-1, where p is the n-th Mersenne prime A000668(n).

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