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 A139243 #16 Oct 20 2023 15:54:13 %S A139243 5,18,456,1056,29184,67584,1867776,130154496,270532608,33420214272, %T A139243 481573208064,1133871366144,31336081391616,2183630092763136, %U A139243 139646772820574208,290482175965396992,35884681830888112128,517085294816170868736,1217485108864830406656 %N A139243 Second differences of Mersenne numbers A001348, divided by 4. %H A139243 Paolo Xausa, <a href="/A139243/b139243.txt">Table of n, a(n) for n = 1..450</a> %F A139243 a(n) = A139241(n)/4 = A139242(n)/2. %t A139243 Differences[2^Prime[Range[25]]-1,2]/4 (* _Paolo Xausa_, Oct 20 2023 *) %Y A139243 Cf. A001348, A139237, A139239, A139240, A139241, A139242. %K A139243 easy,nonn %O A139243 1,1 %A A139243 _Omar E. Pol_, Apr 19 2008 %E A139243 More terms from _Alois P. Heinz_, Mar 13 2020