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A032703 n prefixed by '3' and followed by '1' is a prime. 1
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 (list; graph; refs; listen; history; text; internal format)
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

Sequence in context: A047906 A342776 A104641 * A234904 A284806 A125821

Adjacent sequences:  A032700 A032701 A032702 * A032704 A032705 A032706

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, May 15 1998

EXTENSIONS

Offset changed to 1 by Robert Israel, Oct 22 2018

STATUS

approved

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Last modified October 20 10:43 EDT 2021. Contains 348100 sequences. (Running on oeis4.)