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A337480 Numbers k such that exactly one of 6*k + 5 and 12*k + 5 is prime. 2
6, 12, 13, 17, 18, 19, 23, 26, 27, 28, 31, 33, 39, 41, 44, 47, 48, 49, 52, 53, 54, 56, 57, 59, 67, 68, 69, 74, 76, 78, 83, 86, 87, 88, 91, 93, 94, 97, 101, 109, 112, 114, 116, 117, 124, 126, 128, 129, 132, 133, 137, 139, 141, 144, 146, 147, 151, 154, 159, 161 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..10000

EXAMPLE

a(5) = 18 is a term because 6*18 + 5 = 113 is prime; but 12*18 + 5 = 221 = (13*17) is a composite number.

a(8) = 26 is a term because 6*26 + 5 = 161 = (7*23) is a composite number; but 12*26 + 5 = 317 is prime.

MAPLE

A337480:=k->`if`(isprime(6*k+5) xor isprime(12*k+5), k, NULL): seq(A337480(k), k=1..1000);

MATHEMATICA

Select[Range[0, 250], Xor[PrimeQ[6 # + 5], PrimeQ[12 # + 5]] &]

PROG

(PARI) for(k=1, 1000, if (bitxor(isprime(6*k+5), isprime(12*k+5)), print1(k, ", ")));

CROSSREFS

Cf. A063913, A145487, A145490, A172287.

Sequence in context: A335485 A004749 A107687 * A297258 A296702 A297135

Adjacent sequences:  A337477 A337478 A337479 * A337481 A337482 A337483

KEYWORD

nonn

AUTHOR

K. D. Bajpai, Aug 28 2020

STATUS

approved

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Last modified November 28 13:47 EST 2021. Contains 349413 sequences. (Running on oeis4.)