A135076 Primes appearing in A001370.

2, 7, 5, 11, 13, 7, 19, 19, 29, 31, 41, 37, 29, 43, 41, 37, 47, 61, 59, 67, 71, 61, 73, 79, 89, 109, 103, 89, 109, 107, 107, 113, 139, 151, 127, 137, 107, 113, 167, 173, 167, 181, 191, 173, 193, 223, 233, 211, 199, 229, 251, 239, 281, 251, 277, 281, 239, 241, 239, 269

Offset: 1

Author

Zak Seidov, Nov 18 2007

Keywords

• base
• nonn

Examples

			a(1)=2 because with s=A076203(1)=1, 2^s=2 and sod(2)=2; sod(x)=sum of digits of x;
a(2)=7 because with s=A076203(2)=4, 2^s=16 and sod(16)=7.
a(7)=9 because with s=A076203(7)=12, 2^s=4096 and sod(4096)=19.
a(8)=9 because with s=A076203(8)=18, 2^s=262144 and sod(262144)=19.
		

Links

• Zak Seidov, Table of n, a(n) for n = 1..1000.

Crossrefs

Cf. A001370, A076203.

Programs

PARI

lista(nn) = {for (n=1, nn, sd = sumdigits(2^n); if (isprime(sd), print1(sd, ", ")););} \\ Michel Marcus, Oct 13 2013

Formula

a(n)=A007953(2^A076203(n)).

Extensions

Name corrected by Michel Marcus, Oct 13 2013