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 A227979 #29 Feb 16 2025 08:33:20
%S A227979 2,4,6,8,9,14,16,18,22,23,24,32,33,36,38,42,44,46,47,54,56,59,62,64,
%T A227979 66,69,71,72,77,81,83,86,88,92,94,96,98,99,107,114,118,121,126,128,
%U A227979 131,132,134,138,141,142,144,152,154,158,161,162,166,167,168,177
%N A227979 Integers not of the form (a^k+b^k)/(a+b) for any positive integer values of a, b, k with b > a.
%C A227979 This form, (a^k+b^k)/(a+b), is a generalization of the Fermat numbers.
%C A227979 Not all integers are in this set.
%C A227979 See A229791 for the complement of this sequence.
%H A227979 Robert Price, <a href="/A227979/b227979.txt">Table of n, a(n) for n = 1..66</a>
%H A227979 J. Brillhart et al., <a href="http://dx.doi.org/10.1090/conm/022">Factorizations of b^n +- 1</a>, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
%H A227979 H. Dubner and T. Granlund, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL3/DUBNER/dubner.html">Primes of the Form (b^n+1)/(b+1)</a>, J. Integer Sequences, 3 (2000), #P00.2.7.
%H A227979 H. Lifchitz, <a href="http://www.primenumbers.net/Henri/us/MersFermus.htm">Mersenne and Fermat primes field</a>
%H A227979 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Repunit.html">Repunit</a>.
%t A227979 limit=200; lst = {}; Do[p = (a^k + b^k)/(a + b); If[p <= limit && IntegerQ[p], AppendTo[lst, p]], {k, Log[2,3*limit+1]}, {b, 2, limit*2}, {a, b-1}]; Complement[Range[limit], Union[lst]]
%Y A227979 A few of the sequences using this form that identify primes are A000978, A007658, A057469, A128066, A057171, A082387, A122853, A128335.
%K A227979 nonn
%O A227979 1,1
%A A227979 _Robert Price_, Sep 30 2013