A097386 Numbers n such that (largest digit of n)^(smallest digit of n) + n is prime.

1, 10, 21, 30, 32, 40, 43, 60, 61, 65, 70, 81, 92, 100, 102, 106, 108, 130, 150, 152, 161, 172, 174, 180, 183, 185, 190, 210, 221, 232, 240, 250, 252, 270, 280, 283, 285, 292, 298, 306, 310, 322, 330, 354, 361, 372, 376, 381, 394, 400, 408, 420, 423, 430, 460

Offset: 1

Author

Jason Earls, Aug 18 2004

Keywords

• base
• easy
• nonn

Comments

No term ends in 9. Conjecture: Let f(x)=(largest digit of x)^(smallest digit of x) + x. There are infinitely many positive integers n such that f(n) and f(n+1) are both prime; see A097387.

Examples

			1272 is in the sequence because 7^2 + 1272 = 1321, a prime.
		

Crossrefs

Cf. A054054, A054055, A097385, A097387.

Programs

Mathematica

okQ[n_]:=Module[{idn=IntegerDigits[n]},PrimeQ[Max[idn]^Min[idn]+n]]
Select[Range[500],okQ] (* Harvey P. Dale, Dec 11 2010 *)

Extensions

Corrected by T. D. Noe, Oct 25 2006