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 A143012 #12 Mar 11 2019 03:07:00 %S A143012 151,2359,599479,9588151,2454285751,39268347319,10052678938039, %T A143012 41175768098368951,658812288653553079,2698495133088002829751, %U A143012 690814754065816531725751,11053036065049294753459639,2829577232652317876553477559,11589948344943812957569751412151 %N A143012 Numbers of the form (4^p + 2^p + 1)/7, where p > 3 is prime. %C A143012 If 8^p-1 is squarefree then the terms of the sequence are either primes (A000040) or overpseudoprimes to base 2 (A141232). In particular, composite numbers of the sequence are strong pseudoprimes to base 2 (A001262). E.g., a(5)=2454285751 is A001262(1828). %H A143012 V. Shevelev, <a href="http://arxiv.org/abs/0807.2332">Process of "primoverization" of numbers of the form a^n-1</a>, arXiv:0807.2332 [math.NT], 2008. %p A143012 p:=ithprime: seq((4^p(n)+2^p(n)+1)*1/7, n=3..14); # _Emeric Deutsch_, Aug 16 2008 %t A143012 (4^#+2^#+1)/7&/@Prime[Range[3,30]] (* _Harvey P. Dale_, Feb 19 2013 *) %Y A143012 Cf. A001262, A141232, A000040, A126614. %K A143012 nonn %O A143012 1,1 %A A143012 _Vladimir Shevelev_, Jul 15 2008, Jul 21 2008 %E A143012 Extended by _Emeric Deutsch_, Aug 16 2008 %E A143012 More terms from _Harvey P. Dale_, Feb 19 2013