A139294 a(n) = 2^(2p - 1), where p is the n-th Mersenne prime A000668(n).

32, 8192, 2305843009213693952, 14474011154664524427946373126085988481658748083205070504932198000989141204992

Offset

1,1

Comments

Next terms have 4932, 78913, 315652, 1292913986, and 1388255822130839283 decimal digits. - Jens Kruse Andersen, Jul 14 2014

Links

Table of n, a(n) for n=1..4.

Formula

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

Mathematica

A000668 := Select[2^Range[500] - 1, PrimeQ]; Table[2^(2*A000668[[n]] - 1), {n, 1, 5}] (* G. C. Greubel, Oct 03 2017 *)
a[n_] := 2^(2^(MersennePrimeExponent[n] + 1) - 3); Array[a, 4] (* Amiram Eldar, Jul 10 2025 *)

Prog

(PARI) \p 100
print1("a(n): "); forprime(q=2, 7, p=2^q-1; if(isprime(p), print1(2^(2*p-1)", ")));
print1("\nNumber of digits in a(n): "); forprime(q=2, 127, p=2^q-1; if(isprime(p), print1(ceil((2*p-1)*log(2)/log(10))", "))) \\ Jens Kruse Andersen, Jul 14 2014

Crossrefs

Cf. A000079, A000668, A139286, A139295, A139296, A139297, A139298, A139299, A139300, A139301, A139302, A139303, A139304, A139305, A139306.

Sequence in context: A248001 A159679 A139568 * A227603 A327130 A231035

Adjacent sequences: A139291 A139292 A139293 * A139295 A139296 A139297

Keyword

nonn

Author

Omar E. Pol, Apr 13 2008

Status

approved