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 A326655 #10 Jul 24 2019 06:03:52 %S A326655 1,3,4,6,9,15,18,33,138,204,219,267,1104,1408,1584,1956,17175,21147, %T A326655 24075,27396,27591,40095,354984,400989,916248,1145805,2541153,5414673 %N A326655 Numbers k such that 3*4^k+1 is prime. %C A326655 One half of the even terms in A002253. %Y A326655 Numbers k such that r*(r+1)^k+1 is prime: A003306 (r=2), this sequence (r=3), A204322 (r=4), A247260 (r=5), A245241 (r=6), A269544 (r=7), A056799 (r=8), A056797 (r=9), A057462 (r=10), A251259 (r=11). %K A326655 nonn,more %O A326655 1,2 %A A326655 _Richard N. Smith_, Jul 16 2019