cp's OEIS Frontend

A379865 Number of base 10 digits of 2^(p-1)*(2^p-1) where p = prime(n).

%I A379865 #19 Jan 08 2025 09:26:57
%S A379865 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 A379865 61,62,65,66,68,77,79,83,84,90,91,95,98,101,104,108,109,115,116,119,
%U A379865 120,127,134,137,138,140,144,145,151,155,159,162,163,167,169,171,177
%N A379865 Number of base 10 digits of 2^(p-1)*(2^p-1) where p = prime(n).
%H A379865 Paolo Xausa, <a href="/A379865/b379865.txt">Table of n, a(n) for n = 1..10000</a>
%F A379865 a(n) = A055642(A060286(n)).
%t A379865 A379865[n_] := IntegerLength[2^(# - 1)*(2^# - 1)] & [Prime[n]];
%t A379865 Array[A379865, 100] (* _Paolo Xausa_, Jan 08 2025 *)
%o A379865 (Python)
%o A379865 from sympy import prime
%o A379865 def a(n):
%o A379865   p = prime(n)
%o A379865   return len(str((1 << (p-1)) * ((1 << p) - 1)))
%o A379865 print([a(n) for n in range(1,63)])
%Y A379865 Cf. A034887, A055642, A060286.
%K A379865 nonn,easy,base
%O A379865 1,2
%A A379865 _Darío Clavijo_, Jan 04 2025