A139750 Numbers n such that d_1^1 + ... + d_r^r is a prime number, where d_i are the digits of n (n = d_1, d_2, ..., d_r).

2, 3, 5, 7, 11, 12, 14, 16, 20, 21, 23, 29, 30, 32, 34, 38, 41, 43, 45, 47, 50, 56, 61, 65, 70, 72, 74, 76, 78, 83, 89, 92, 98, 101, 110, 111, 113, 115, 120, 122, 131, 133, 137, 139, 140, 146, 153, 155, 160, 164, 182, 186, 188, 191, 193, 199, 200, 201, 203, 205, 210

Offset: 1

Author

Ctibor O. Zizka, May 19 2008

Keywords

• base
• easy
• nonn
• less

Examples

			1^1+8^2+8^3 = 577 is prime. Thus 188 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. A139752.

Programs

Mathematica

dpnQ[n_]:=Module[{idn=IntegerDigits[n]},PrimeQ[Total[idn^Range[ Length[idn]]]]]; Select[Range[300],dpnQ] (* Harvey P. Dale, Mar 26 2012 *)

PARI

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

Extensions

Edited and extended by Klaus Brockhaus, May 21 2008