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 A239714 #13 Apr 29 2014 23:12:34 %S A239714 19,67,79,271,1039,1087,1279,4099,4111,4159,5119,16447,20479,65539, %T A239714 65551,65599,81919,262147,262399,263167,266239,1049599,1114111, %U A239714 1310719,4194319,4194559,4195327,16842751,17825791,67108879,268435459,268435711,272629759,1073741827,1073741839,1073758207 %N A239714 Primes of the form m = 4^i + 4^j - 1, where i > j >= 0. %C A239714 The base-4 representation of a term 4^i + 4^j - 1 has base-4 digital sum = 1 + 3*j == 1 (mod 3). %C A239714 In base-4 representation the first terms are 103, 1003, 1033, 10033, 100033, 100333, 103333, 1000003, 1000033, 1000333, 1033333, 10000333, 10333333, 100000003, 100000033, 100000333, 103333333, 1000000003, 1000003333, 1000033333, ... %C A239714 Numbers m which satisfy m = 4^i + 4^j + 1 are never primes, since the base-4 digital sum of m is 3, and thus, m is divisible by 3. %H A239714 Hieronymus Fischer, <a href="/A239714/b239714.txt">Table of n, a(n) for n = 1..111</a> %e A239714 a(1) = 19, since 19 = 4^2 + 4^1 - 1 is prime. %e A239714 a(4) = 271, since 271 = 4^4 + 4^2 - 1 is prime. %o A239714 (Smalltalk) %o A239714 A239714 %o A239714 "Answer an array of the first n terms of A239714. %o A239714 Uses method primesWhichAreDistinctPowersOf: b withOffset: d from A239712. %o A239714 Usage: n A239714 %o A239714 Answer: #(19 67 79 ... ) [a(1) ... a(n)]" %o A239714 ^self primesWhichAreDistinctPowersOf: 4 withOffset: -1 %Y A239714 Cf. A234310. %K A239714 nonn %O A239714 1,1 %A A239714 _Hieronymus Fischer_, Apr 14 2014