Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #10 May 13 2020 07:04:14
%S 1,2,2,2,2,2,2,2,4,4,4,8,8,16,4,4,8,2,8,24,8,4,16,8,8,4,16,8,8,6,8,16,
%T 64,4,4,8,8,16,16,2,8,8,64,64,8,4,8,32,8,2,8,8,16,64,8,8,32,8,32,2,8,
%U 64,32,16,8,32,8,8,32,16,64,64,8,64,4,4,16,2
%N a(n) = the number of divisors of 33...31, with n 3s.
%C The first seven 33...31 numbers are prime, so those terms are 2. - _Don Reble_, Oct 26 2006
%H Amiram Eldar, <a href="/A105267/b105267.txt">Table of n, a(n) for n = 0..203</a>
%F a(n) = A000005(A033175(n)). - _Amiram Eldar_, May 13 2020
%t a[n_] := DivisorSigma[0, (10^(n + 1) - 7)/3]; Array[a, 30, 0] (* _Amiram Eldar_, May 13 2020 *)
%o (PARI) a(n) = numdiv((10^(n + 1) - 7)/3); \\ _Michel Marcus_, May 13 2020
%Y Cf. A000005, A051200, A033175, A104484.
%K nonn
%O 0,2
%A _Parthasarathy Nambi_, Apr 29 2005
%E More terms from _Don Reble_, Oct 26 2006