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 A126614 #42 Apr 22 2025 17:49:35
%S A126614 3,11,43,683,2731,43691,174763,2796203,178956971,715827883,
%T A126614 45812984491,733007751851,2932031007403,46912496118443,
%U A126614 3002399751580331,192153584101141163,768614336404564651,49191317529892137643,787061080478274202283,3148244321913096809131
%N A126614 a(n) = (2^prime(n) + 1)/3.
%C A126614 If p - 1 is squarefree, the multiplicative order of 2 modulo a(n) is 2p. - _Vladimir Shevelev_, Jul 15 2008
%C A126614 The prime numbers in this sequence are the Wagstaff primes (A000979). - _Omar E. Pol_, Nov 05 2013
%H A126614 Vincenzo Librandi, <a href="/A126614/b126614.txt">Table of n, a(n) for n = 2..200</a>
%F A126614 a(n) = A001045(A000040(n)). - _Alois P. Heinz_, Apr 14 2025
%e A126614 a(2) = (2^prime(2) + 1)/3 = (2^3 + 1)/3 = 9/3 = 3.
%e A126614 a(3) = (2^prime(3) + 1)/3 = (2^5 + 1)/3 = 33/3 = 11.
%e A126614 a(4) = (2^prime(4) + 1)/3 = (2^7 + 1)/3 = 129/3 = 43.
%t A126614 Table[(2^Prime[n] + 1)/3, {n, 2, 20}]
%o A126614 (Magma) [(2^NthPrime(n)+1)/3: n in [2..20]]; // _Vincenzo Librandi_, Mar 29 2012
%o A126614 (PARI) a(n)=2^prime(n)\/3 \\ _Charles R Greathouse IV_, Mar 29 2012
%o A126614 (PARI) vecextract(apply(p->2^p\/3,primes(100)),"2..") \\ _Charles R Greathouse IV_, Mar 29 2012
%Y A126614 Cf. A000040, A000979, A000978, A001045, A124400.
%K A126614 nonn
%O A126614 2,1
%A A126614 _Artur Jasinski_, Feb 09 2007