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A032731 Numbers k such that k prefixed by '6' and followed by '9' is a prime. 0
1, 5, 19, 22, 26, 29, 32, 35, 37, 38, 44, 46, 52, 56, 59, 61, 65, 67, 68, 70, 71, 77, 82, 86, 89, 94, 95, 109, 112, 116, 133, 137, 140, 146, 151, 155, 160, 172, 181, 187, 190, 194, 197, 203, 209, 211, 212, 218, 221, 229, 245, 253, 254, 263, 265, 281, 286, 292 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..58.

MATHEMATICA

Select[Range@300, PrimeQ@FromDigits@Flatten[{6, IntegerDigits@#, 9}]&] (* Giorgos Kalogeropoulos, Jul 28 2021 *)

PROG

(Python)

from sympy import isprime

def ok(n): return isprime(int('6'+str(n)+'9'))

print(list(filter(ok, range(293)))) # Michael S. Branicky, Jul 28 2021

CROSSREFS

Subsequence of A001651 (not divisible by 3).

Sequence in context: A337401 A338127 A243018 * A275954 A087840 A074229

Adjacent sequences:  A032728 A032729 A032730 * A032732 A032733 A032734

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, May 15 1998

STATUS

approved

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Last modified October 22 13:49 EDT 2021. Contains 348170 sequences. (Running on oeis4.)