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A096818 Exponents n such that 2^n-13 is prime. 16
4, 5, 9, 13, 17, 57, 105, 137, 3217, 3229, 4233, 6097, 8757, 11457, 12073, 15425, 40117, 45357, 334809 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Except the first term 4, all terms are odd since for even n, 2^n-13 is divisible by 3.

LINKS

Table of n, a(n) for n=1..19.

Search for 2^n-13, PRP Top Records

F. Firoozbakht, M. F. Hasler, Variations on Euclid's formula for Perfect Numbers, JIS 13 (2010) #10.3.1.

EXAMPLE

n=5: 32-13=23 is prime.

MATHEMATICA

Select[Range[4, 20000], PrimeQ[2^#-13]&] (* Vladimir Joseph Stephan Orlovsky, Feb 27 2011*)

CROSSREFS

Exponents for primes of 2^n-d form: A000043 (d=1), A050414 (d=3), A059608 (d=5), A059609 (d=7), A059610 (d=9), A096817 (d=11), A096818 (d=13), A059612 (d=15), A059611 (d=17), A096819 (d=19), A096820 (d=21).

Cf. A096502

Sequence in context: A331531 A328223 A116045 * A282467 A318980 A226622

Adjacent sequences:  A096815 A096816 A096817 * A096819 A096820 A096821

KEYWORD

nonn,more

AUTHOR

Labos Elemer, Jul 13 2004

EXTENSIONS

a(16) from Max Alekseyev, a(17)-a(18) from Henri Lifchitz, a(19) from Lelio R Paula, added by Max Alekseyev, Feb 09 2012

STATUS

approved

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Last modified May 8 08:51 EDT 2021. Contains 343666 sequences. (Running on oeis4.)