This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A139480 #18 Oct 17 2024 08:26:42 %S A139480 0,2,4,10,14,16,28,58,86,104,124,518,604,1276,2200,2278,3214,4250, %T A139480 4420,9686,9938,11210,19934,21698,23206,44494,86240,110500,132046, %U A139480 216088,756836,859430,1257784,1398266,2976218,3021374,6972590,13466914,20996008,24036580,25964948 %N A139480 a(n) = A000043(n) - 3. %C A139480 2^a(n)-1 is divisible by 3. For (2^a(n)-1)/3 see A124477. %C A139480 For a(n)/2 see A139481. %H A139480 Amiram Eldar, <a href="/A139480/b139480.txt">Table of n, a(n) for n = 2..48</a> %t A139480 MersennePrimeExponent[Range[2, 48]] - 3 (* _Amiram Eldar_, Oct 17 2024 *) %Y A139480 Cf. A000043, A000668, A124477, A139479, A139481. %K A139480 nonn %O A139480 2,2 %A A139480 _Artur Jasinski_, Apr 22 2008 %E A139480 Definition corrected by _Omar E. Pol_, May 23 2008 %E A139480 Edited by _N. J. A. Sloane_, May 23 2008 %E A139480 a(40)-a(42) from _Amiram Eldar_, Oct 17 2024