A212821 Smallest prime p of the form p = 3^n + k, where k has n prime divisors counted with multiplicity.

2, 5, 13, 47, 97, 419, 953, 3019, 7457, 20963, 61609, 189947, 557041, 1614803, 4840313, 14430827, 43276097, 129959363, 388862281, 1165669339, 3493338001, 10471887539, 31395739673

Offset

0,1

Links

Table of n, a(n) for n=0..22.

Example

a(0) = 2 because 2 = 1 (A001222(1) = 0) + 3^0 = 1 + 1;
a(1) = 5 because 5 = 2 (A001222(2) = 1) + 3^1 = 2 + 3;
a(2) = 13 because 13 = 4 (A001222(4) = 2) + 3^2 = 4 + 9;
a(3) = 47 because 47 = 20 (A001222(20) = 3) + 3^3 = 20 + 27;
a(4) = 97 because 97 = 16 (A001222(16) = 4) + 3^4 = 16 + 81;
a(5) = 419 because 419 = 176 (A001222(176) = 5) + 3^5 = 176 + 243.

Prog

(PARI) for(n=0, 30, p=3^n; k=1; while(1, if(bigomega(k)==n && isprime(p+k), print1(p+k, ", "); break, k++))) \\ Colin Barker, Jun 27 2014

Crossrefs

Cf. A001222.

Sequence in context: A079573 A360513 A194635 * A067021 A269068 A098716

Adjacent sequences: A212818 A212819 A212820 * A212822 A212823 A212824

Keyword

nonn

Author

Juri-Stepan Gerasimov, Jul 02 2012

Extensions

More terms from Colin Barker, Jun 27 2014

Status

approved