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a(n) = number of decimal digits of A007505(n).
0

%I #7 Jul 24 2016 21:23:23

%S 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,

%T 250,384,987,1267,1546,2276,3817,4486,5457,5666,7734,7966,12532,15470,

%U 21610,24183,25795,26543,29220,37217,46941,49667,70671,124880,176102,211335,219060,298833,361552,370947,696203,944108,1274988,1833429,3457035,3531640,3580969

%N a(n) = number of decimal digits of A007505(n).

%F a(n) = A055642(A007505(n)). - _Michel Marcus_, Jul 23 2016

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

%K base,nonn

%O 1,3

%A _Zak Seidov_, Jul 21 2016