A138790 Numbers k such that A138793(k) is prime.

61, 946

Offset: 1

Author

Artur Jasinski, Mar 30 2008, Mar 31 2008

Keywords

• nonn
• bref
• hard
• more
• base

Comments

There are no more primes for k <= 5000.

a(3) > 20000. - Robert Price, Mar 24 2015

Examples

			a(1) = 61 because the number 160695...654321 is prime.
		

Crossrefs

Cf. A000422, A116504, A007908, A116505, A138793.

Programs

Mathematica

b = {}; a = {}; Do[w = RealDigits[n]; w = First[w]; Do[AppendTo[a, w[[k]]], {k, 1, Length[w]}]; p = FromDigits[Reverse[a]]; If[PrimeQ[p], Print[n]; AppendTo[b, p]], {n, 1, 2000}]; b (* Artur Jasinski, Mar 30 2008 *)
Select[Range[1, 1000], PrimeQ[lst = {}; Do[lst = Join[lst, IntegerDigits[n]], {n, 1, #}]; FromDigits[Reverse[lst]]] &] (* Robert Price, Mar 24 2015 *)