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A032719 Numbers n such that n prefixed by '2' and followed by '7' is prime. 1
2, 5, 7, 13, 20, 23, 26, 28, 29, 34, 35, 37, 41, 43, 44, 46, 47, 55, 61, 64, 65, 67, 68, 70, 76, 77, 79, 83, 85, 88, 89, 91, 92, 95, 101, 106, 110, 115, 118, 122, 124, 127, 131, 134, 137, 139, 140, 146, 148, 151, 155, 157, 158, 161, 164, 172, 173, 175, 176 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Range[200], PrimeQ[2*10^(IntegerLength[#]+1)+10#+7]&] (* Harvey P. Dale, Dec 10 2016 *)

CROSSREFS

Sequence in context: A262392 A056985 A082182 * A334246 A275287 A261581

Adjacent sequences:  A032716 A032717 A032718 * A032720 A032721 A032722

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, May 15 1998

STATUS

approved

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Last modified May 28 03:04 EDT 2020. Contains 334671 sequences. (Running on oeis4.)