A032705 - OEIS

A032705

Numbers k such that k prefixed by '5' and followed by '1' is prime.

2, 4, 7, 10, 17, 23, 26, 28, 35, 38, 43, 44, 47, 50, 52, 53, 58, 59, 64, 65, 70, 71, 74, 79, 80, 82, 85, 86, 88, 98, 100, 103, 106, 107, 113, 115, 124, 134, 136, 142, 143, 146, 148, 151, 152, 155, 158, 163, 169, 172, 187, 194, 197, 199, 202, 205, 208, 212

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OFFSET

1,1

LINKS

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

MATHEMATICA

Select[Range[0, 212], PrimeQ@FromDigits[Join[{5}, IntegerDigits@#, {1}]]&] (* Giorgos Kalogeropoulos, Jul 28 2021 *)

CROSSREFS

Subsequence of A001651 (not divisible by 3).

Sequence in context: A131752 A062365 A049630 * A332639 A281168 A274352

Adjacent sequences: A032702 A032703 A032704 * A032706 A032707 A032708

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, May 15 1998

STATUS

approved