

A303090


Numbers k such that 5^k + 2*k is a prime.


1



1, 2, 3, 7, 18, 27, 61, 721, 873, 2492, 8713
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OFFSET

1,2


COMMENTS

a(12) > 20000.  Jon E. Schoenfield, Apr 19 2018


LINKS

Table of n, a(n) for n=1..11.


EXAMPLE

1 is a term because 5^1 + 2*1 = 5 + 2 = 7, a prime.
2 is a term because 5^2 + 2*2 = 25 + 4 = 29, a prime.
3 is a term because 5^3 + 2*3 = 125 + 6 = 131, a prime.


MAPLE

a:=k>`if`(isprime(5^k+2*k), k, NULL): seq(a(k), k=1..5500);


PROG

(GAP) Filtered([1..700], k>IsPrime(5^k+2*k));
(PARI) isok(k) = isprime(5^k + 2*k); \\ Altug Alkan, Apr 19 2018


CROSSREFS

Cf. A299642, A299643, A297663.
Sequence in context: A295509 A225747 A058334 * A131093 A002864 A005248
Adjacent sequences: A303087 A303088 A303089 * A303091 A303092 A303093


KEYWORD

nonn,more


AUTHOR

Muniru A Asiru, Apr 18 2018


EXTENSIONS

a(11) from Jon E. Schoenfield, Apr 18 2018


STATUS

approved



