A032704 Numbers k such that k prefixed by '4' and followed by '1' is prime.

0, 2, 3, 6, 9, 11, 20, 21, 23, 24, 26, 27, 39, 42, 44, 45, 48, 56, 59, 62, 65, 69, 72, 75, 80, 83, 86, 87, 93, 95, 101, 105, 108, 113, 114, 116, 120, 122, 123, 128, 134, 135, 138, 141, 149, 152, 161, 162, 164, 165, 168, 176, 177, 180, 185, 191, 194, 198, 206

Offset: 1

Author

Patrick De Geest, May 15 1998

Keywords

• nonn
• base
• changed

Links

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

Crossrefs

Cf. A032702-A032733.

Programs

Mathematica

Select[Range[0,250],PrimeQ[FromDigits[Join[{4},IntegerDigits[#],{1}]]]&] (* Harvey P. Dale, Aug 30 2025 *)

Extensions

Offset changed by Andrew Howroyd, Aug 11 2024