A139749 Numbers n such that d_1^r + ... + d_r^1 is a prime number, where d_i are the digits of n (n = d_1, ..., d_r).

2, 3, 5, 7, 11, 12, 14, 16, 21, 23, 27, 29, 32, 34, 38, 41, 43, 47, 54, 56, 61, 65, 67, 74, 83, 87, 89, 92, 98, 101, 102, 104, 106, 110, 111, 113, 115, 119, 120, 122, 126, 128, 131, 133, 137, 139, 140, 142, 146, 153, 155, 160, 164, 166, 173, 179, 182, 186, 188, 191

Offset: 1

Author

Ctibor O. Zizka, May 19 2008

Keywords

• base
• easy
• nonn
• less

Examples

			1^3 + 3^2 + 7^1 = 17 is prime. Thus 137 is a member of this sequence. - _Derek Orr_, Jul 13 2014
		

Links

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

Crossrefs

Cf. A139751.

Programs

Mathematica

Select[Range[200],PrimeQ[Total[IntegerDigits[#]^Range[IntegerLength[#],1,-1]]]&] (* Harvey P. Dale, Aug 14 2019 *)

PARI

for(n=1,10^3,d=digits(n);s=sum(i=1,#d,d[i]^(#d-i+1));if(isprime(s),print1(n,", "))) \\ Derek Orr, Jul 13 2014

Extensions

Edited and extended by Klaus Brockhaus, May 21 2008