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 A139242 #15 Oct 20 2023 15:53:49 %S A139242 10,36,912,2112,58368,135168,3735552,260308992,541065216,66840428544, %T A139242 963146416128,2267742732288,62672162783232,4367260185526272, %U A139242 279293545641148416,580964351930793984,71769363661776224256,1034170589632341737472,2434970217729660813312 %N A139242 Second differences of Mersenne numbers A001348, divided by 2. %H A139242 Paolo Xausa, <a href="/A139242/b139242.txt">Table of n, a(n) for n = 1..450</a> %F A139242 a(n) = A139241(n)/2. %t A139242 Differences[2^Prime[Range[25]]-1,2]/2 (* _Paolo Xausa_, Oct 20 2023 *) %Y A139242 Cf. A001348, A139233, A139237, A139238, A139239, A139240, A139241, A139243. %K A139242 easy,nonn %O A139242 1,1 %A A139242 _Omar E. Pol_, Apr 19 2008 %E A139242 Corrected and extended by _Alois P. Heinz_, Mar 13 2020