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 A139115 #21 Oct 18 2024 11:42:03 %S A139115 2,6,20,42,156,272,342,930,3660,7832,11342,16002,270920,367842, %T A139115 1634562,4851006,5200680,10345872,18083756,19558506,93867032,98813540, %U A139115 125720156,397464032,470911700,538634472,1979938512,7437768806,12210802506 %N A139115 a(n) = p*(p - 1), where p is A000043(n). %H A139115 Amiram Eldar, <a href="/A139115/b139115.txt">Table of n, a(n) for n = 1..48</a> (terms 1..47 from Harvey P. Dale) %F A139115 a(n) = A000043(n)*(A000043(n) - 1). %t A139115 #(#-1)&/@MersennePrimeExponent[Range[30]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jan 15 2020 *) %Y A139115 Cf. A000043, A036689, A139306, A139307, A139116, A139223, A139224, A139225, A139226. %K A139115 nonn %O A139115 1,1 %A A139115 _Omar E. Pol_, May 10 2008 %E A139115 More terms from _Vincenzo Librandi_, May 11 2010