A099191 Smallest prime p such that p+n is twice its reversal, or 0 if impossible.

73, 2, 3, 0, 5, 0, 7, 0, 0, 0, 11, 0, 211, 0, 0, 0, 53, 0, 613, 0, 0, 0, 0, 0, 43, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 23, 0, 241, 0, 0, 0, 0, 0, 13, 0, 0, 0, 251, 0, 0, 0, 0, 0, 653, 0, 97, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 271, 0, 0, 0, 0, 0, 673, 0, 0, 0, 281, 0, 67, 0, 0, 0, 683, 0, 0, 0, 0

Offset: 1

Author

Robert G. Wilson v, Oct 01 2004

Keywords

• base
• nonn

Examples

			a(13) = 211 since 211+13 = 224 = 2*112. a(25) = 43 since 25+43 = 68 = 2*34.
		

Crossrefs

Cf. A099190.

Programs

Mathematica

f[n_] := Block[{k = 1}, While[p = Prime[k]; p + n != 2FromDigits[ Reverse[ IntegerDigits[ p]]] && k < 10^6, k++ ]; If[k == 10^6, 0, Prime[k]]]; Table[ f[n], {n, 75}]