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 A139241 #12 Oct 20 2023 15:53:44 %S A139241 20,72,1824,4224,116736,270336,7471104,520617984,1082130432, %T A139241 133680857088,1926292832256,4535485464576,125344325566464, %U A139241 8734520371052544,558587091282296832,1161928703861587968,143538727323552448512,2068341179264683474944,4869940435459321626624 %N A139241 Second differences of Mersenne numbers A001348. %H A139241 Paolo Xausa, <a href="/A139241/b139241.txt">Table of n, a(n) for n = 1..450</a> %F A139241 a(n) = 2^prime(n+2)-2^(prime(n+1)+1)+2^prime(n). - _Michel Marcus_, Mar 13 2020 %t A139241 Differences[2^Prime[Range[25]]-1,2] (* _Paolo Xausa_, Oct 20 2023 *) %o A139241 (PARI) a(n) = 2^prime(n+2)-2^(prime(n+1)+1)+2^prime(n); \\ _Michel Marcus_, Mar 13 2020 %Y A139241 Cf. A001348, A139230, A139232, A139236, A139238, A139242, A139243. %K A139241 easy,nonn %O A139241 1,1 %A A139241 _Omar E. Pol_, Apr 19 2008 %E A139241 More terms from _Alois P. Heinz_, Mar 13 2020