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 #13 Oct 07 2014 16:51:27
%S 0,3,8,48,121,312,16104,122640,7596480,61171656,4093181688,
%T 2366564736720,19924948267224,12169835294351280,889585277491970400,
%U 7633882962663652968,565719454445904325272,365721616371321130128240,239498069351503974657030696,2084811062715550992506283600
%N Numbers of the form (3^k - 3)/k.
%C Generated by k: 1, 2, 3, 5, 6, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 66, 67, ...
%C Subsequence of A246445.
%e 121 is in this sequence because (3^k - 3)/k = (3^6 - 3)/6 = 121.
%Y Cf. A000040, A005935, A064535 (with form (2^k - 2)/k), A122780 (nonprimes k in a(n)), A246445, A247307 (with form (4^k - 4)/k).
%K nonn
%O 1,2
%A _Juri-Stepan Gerasimov_, Sep 09 2014