A109372 Numbers k such that k * (sum of the digits of k raised to their own power) + 1 is prime.

1, 11, 12, 20, 33, 34, 35, 36, 52, 64, 75, 79, 84, 94, 95, 102, 104, 110, 112, 121, 138, 163, 167, 170, 174, 184, 192, 200, 217, 231, 235, 246, 250, 255, 256, 321, 336, 343, 352, 354, 365, 390, 394, 414, 415, 420, 422, 438, 440, 446, 450, 455, 462, 471, 474

Offset: 1

Author

Jason Earls, Aug 24 2005

Keywords

• base
• easy
• nonn

Comments

A zero digit raised to the zeroth power is treated as equaling one. - Harvey P. Dale, Feb 19 2013

Examples

			a(7)=35 because 35*(3^3 + 5^5) + 1 = 110321 is prime.
		

Links

• Eric M. Schmidt, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A045503.

Programs

Mathematica

ndnQ[n_]:=Module[{idn=IntegerDigits[n]/.{0->1}},PrimeQ[n*Total[idn^idn]+1]]; Select[Range[500],ndnQ] (* Harvey P. Dale, Feb 19 2013 *)

PARI

isok(n) = my(d = digits(n)); isprime(n*sum(i=1,#d, d[i]^d[i])+1); \\ Michel Marcus, Sep 16 2018