A073041 n*R(n)-1 is prime, where R(n) is reverse of n.

2, 12, 21, 30, 36, 60, 63, 90, 114, 132, 150, 162, 174, 192, 198, 204, 231, 237, 240, 246, 255, 261, 264, 291, 306, 330, 360, 378, 390, 402, 411, 420, 438, 447, 456, 462, 471, 477, 495, 510, 552, 588, 594, 603, 609, 627, 630, 642, 654, 669, 690, 726, 732

Offset: 1

Author

Shyam Sunder Gupta, Aug 23 2002

Keywords

• easy
• base
• nonn

Comments

From Robert Israel, Jul 25 2019: (Start)

If n is in the sequence and is not divisible by 10, then A004086(n) is in the sequence.

All terms except 2 are divisible by 3. (End)

Examples

			12 is a term because 12*21-1=251 is prime.
		

Links

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

Crossrefs

Cf. A004086, A061205.

Programs

Maple

revdigs:= proc(n) local L,i;
  L:= convert(n,base,10);
  add(L[-i]*10^(i-1),i=1..nops(L))
end proc:
select(t -> isprime(t*revdigs(t)-1), [$1..1000]); # Robert Israel, Jul 25 2019

Mathematica

Select[Range[800],PrimeQ[# IntegerReverse[#]-1]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 05 2020 *)