A219049 - OEIS

A219049

Numbers k such that 3^k - 32 is prime.

5, 8, 18, 21, 69, 84, 181, 216, 461, 642, 672, 2413, 3681, 5666, 12281, 14949, 19508, 27817, 34061, 43236, 43733, 81828

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OFFSET

1,1

COMMENTS

a(23) > 2*10^5. - Robert Price, Dec 22 2013

LINKS

Table of n, a(n) for n=1..22.

EXAMPLE

3^5 - 32 = 211 (prime), so 5 is in the sequence.

MATHEMATICA

Do[If[PrimeQ[3^n - 32], Print[n]], {n, 10000}]

PROG

(PARI) is(n)=isprime(3^n-32) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Cf. Sequences of numbers k such that 3^k + m is prime:

(m = 2) A051783, (m = -2) A014224, (m = 4) A058958, (m = -4) A058959,

(m = 8) A217136, (m = -8) A217135, (m = 10) A217137, (m = -10) A217347,

(m = 14) A219035, (m = -14) A219038, (m = 16) A205647, (m = -16) A219039,

(m = 20) A219040, (m = -20) A219041, (m = 22) A219042, (m = -22) A219043,

(m = 26) A219044, (m = -26) A219045, (m = 28) A219046, (m = -28) A219047,

(m = 32) A219048, (m = -32) A219049, (m = 34) A219050, (m = -34) A219051. Note that if m is a multiple of 3, 3^k + m is also a multiple of 3 (for k greater than 0), and as such isn't prime.

Sequence in context: A291752 A237276 A155086 * A245534 A302393 A342804

Adjacent sequences: A219046 A219047 A219048 * A219050 A219051 A219052

KEYWORD

nonn,more

AUTHOR

Nicolas M. Perrault, Nov 10 2012

EXTENSIONS

a(15)-a(22) from Robert Price, Dec 22 2013

STATUS

approved