A032703 Numbers k such that k prefixed by '3' and followed by '1' is prime.

1, 3, 12, 18, 19, 22, 25, 27, 30, 33, 36, 37, 39, 46, 49, 51, 54, 57, 58, 63, 67, 69, 70, 76, 82, 85, 88, 91, 93, 105, 108, 109, 112, 115, 118, 123, 127, 132, 139, 148, 151, 153, 154, 160, 172, 174, 175, 177, 189, 198, 199, 205, 214, 219, 225, 226, 232, 234

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

seq(op(select(x -> isprime(3*10^d+10*x+1), [$10^(d-2)..10^(d-1)-1])), d=2..4); # Robert Israel, Oct 22 2018

Mathematica

Select[Range[250], PrimeQ[FromDigits[Join[{3}, IntegerDigits[#], {1}]]]&]  (* Harvey P. Dale, Mar 28 2011 *)

Crossrefs

Cf. A032702-A032733.

Sequence in context: A047906 A342776 A104641 * A234904 A284806 A125821

Adjacent sequences: A032700 A032701 A032702 * A032704 A032705 A032706

Keyword

nonn,base,changed

Author

Patrick De Geest, May 15 1998

Extensions

Offset changed to 1 by Robert Israel, Oct 22 2018

Status

approved