A275247 a(n) = number of decimal digits of A007505(n).

1, 1, 2, 2, 2, 3, 3, 4, 6, 11, 12, 14, 18, 20, 24, 29, 32, 44, 63, 66, 93, 99, 119, 139, 142, 250, 384, 987, 1267, 1546, 2276, 3817, 4486, 5457, 5666, 7734, 7966, 12532, 15470, 21610, 24183, 25795, 26543, 29220, 37217, 46941, 49667, 70671, 124880, 176102, 211335, 219060, 298833, 361552, 370947, 696203, 944108, 1274988, 1833429, 3457035, 3531640, 3580969

Offset: 1

Author

Zak Seidov, Jul 21 2016

Keywords

• base
• nonn

Crossrefs

Cf. A055642, A007505 (primes of form 3*2^n-1), A002235 (numbers n such that 3*2^n-1 is prime).

Formula

a(n) = A055642(A007505(n)). - Michel Marcus, Jul 23 2016