A073805 Numbers k such that 1 + k*R(k) is prime, where R(k) is the reverse of k.

1, 2, 4, 6, 10, 16, 18, 20, 24, 25, 26, 28, 36, 42, 50, 52, 58, 61, 62, 63, 66, 68, 70, 80, 81, 82, 85, 86, 90, 100, 108, 112, 116, 120, 132, 136, 138, 140, 152, 162, 170, 190, 198, 200, 204, 205, 209, 210, 211, 213, 214, 219, 223, 224, 228, 231, 234, 236, 238

Offset: 1

Author

Shyam Sunder Gupta, Aug 23 2002

Keywords

• nonn
• easy
• base
• look

Examples

			16 is a term because 16*61 + 1 = 977 is prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A004086, A061205.

Programs

Maple

rev:= proc(n) local L,i;
  L:= convert(n,base,10);
  add(L[-i]*10^(i-1),i=1..nops(L))
end proc:
filter:= t -> isprime(t*rev(t)+1):
select(filter, [$1..1000]); # Robert Israel, Jul 03 2024

Mathematica

Select[Range[250],PrimeQ[# IntegerReverse[#]+1]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 05 2017 *)