A379865 - OEIS

%I #19 Jan 08 2025 09:26:57

%S 1,2,3,4,7,8,10,12,14,18,19,22,25,26,28,32,36,37,41,43,44,48,50,54,59,

%T 61,62,65,66,68,77,79,83,84,90,91,95,98,101,104,108,109,115,116,119,

%U 120,127,134,137,138,140,144,145,151,155,159,162,163,167,169,171,177

%N Number of base 10 digits of 2^(p-1)*(2^p-1) where p = prime(n).

%H Paolo Xausa, <a href="/A379865/b379865.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A055642(A060286(n)).

%t A379865[n_] := IntegerLength[2^(# - 1)*(2^# - 1)] & [Prime[n]];

%t Array[A379865, 100] (* _Paolo Xausa_, Jan 08 2025 *)

%o (Python)

%o from sympy import prime

%o def a(n):

%o   p = prime(n)

%o   return len(str((1 << (p-1)) * ((1 << p) - 1)))

%o print([a(n) for n in range(1,63)])

%Y Cf. A034887, A055642, A060286.

%K nonn,easy,base

%O 1,2

%A _Darío Clavijo_, Jan 04 2025