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 A139286 #18 May 07 2025 14:58:02 %S A139286 8,32,512,8192,2097152,33554432,8589934592,137438953472, %T A139286 35184372088832,144115188075855872,2305843009213693952, %U A139286 9444732965739290427392,2417851639229258349412352,38685626227668133590597632,9903520314283042199192993792 %N A139286 a(n) = 2^(2*prime(n) - 1). %t A139286 2^(2Prime[Range[20]]-1) (* _Harvey P. Dale_, Dec 01 2017 *) %o A139286 (Magma) [2^(2*p-1): p in PrimesUpTo(200)]; // _Vincenzo Librandi_, Dec 15 2010 %o A139286 (PARI) a(n)=2^(2*prime(n)-1) \\ _Charles R Greathouse IV_, Jul 02 2013 %Y A139286 Cf. A000040, A000079, A076274, A139287, A139288, A139289, A139290, A139291, A139292, A139293, A139294, A139306. %K A139286 nonn,less %O A139286 1,1 %A A139286 _Omar E. Pol_, Apr 13 2008 %E A139286 Corrected and extended by _Harvey P. Dale_, Dec 01 2017