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A139294 2^(2p - 1), where p is a Mersenne prime A000668(n). 19
32, 8192, 2305843009213693952, 14474011154664524427946373126085988481658748083205070504932198000989141204992 (list; graph; refs; listen; history; text; internal format)
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 *)

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

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Last modified October 18 12:18 EDT 2019. Contains 328160 sequences. (Running on oeis4.)