A032719 Numbers k such that k prefixed by '2' and followed by '7' is prime.

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

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

Subsequence of A001651 (not divisible by 3).

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