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 A139239 #8 Oct 20 2023 16:54:52 %S A139239 2,12,48,960,3072,61440,196608,3932160,264241152,805306368, %T A139239 67645734912,1030792151040,3298534883328,65970697666560, %U A139239 4433230883192832,283726776524341248,864691128455135232,72634054790231359488,1106804644422573096960,3541774862152233910272,297509088420787648462848 %N A139239 First differences of Mersenne numbers A001348, divided by 2. %H A139239 Paolo Xausa, <a href="/A139239/b139239.txt">Table of n, a(n) for n = 1..450</a> %F A139239 a(n) = A139238(n)/2. %t A139239 Differences[2^Prime[Range[25]]-1]/2 (* _Paolo Xausa_, Oct 20 2023 *) %Y A139239 Cf. A001348, A139229, A139235, A139238, A139240, A139242. %K A139239 easy,nonn %O A139239 1,1 %A A139239 _Omar E. Pol_, Apr 19 2008 %E A139239 a(10)-a(21) from _Paolo Xausa_, Oct 20 2023