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
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.
Programs
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PARI
lista(nn) = {for (n=1, nn, sd = sumdigits(2^n); if (isprime(sd), print1(sd, ", ")););} \\ Michel Marcus, Oct 13 2013
Extensions
Name corrected by Michel Marcus, Oct 13 2013
Comments