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 A155877 #15 Feb 16 2025 08:33:09
%S A155877 9,11,13,15,23,25,27,37,39,51,263,265,267,277,279,291,517,519,531,771,
%T A155877 65543,65545,65547,65557,65559,65571,65797,65799,65811,66051,131077,
%U A155877 131079,131091,131331,196611,4294967303,4294967305,4294967307
%N A155877 Sums of three Fermat numbers.
%H A155877 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GeneralizedFermatNumber.html">Generalized Fermat Number</a>.
%F A155877 {(2^(2^a) + 1) + (2^(2^b) + 1) + (2^(2^c) + 1)} = {A000215(a) + A000215(b) + A000215(c)}.
%e A155877 a(1) = 3 + 3 + 3 = 9.
%e A155877 a(2) = 3 + 3 + 5 = 11.
%e A155877 a(3) = 3 + 5 + 5 = 13.
%e A155877 a(4) = 5 + 5 + 5 = 15.
%e A155877 a(5) = 3 + 3 + 17 = 23.
%e A155877 a(6) = 3 + 5 + 17 = 25.
%e A155877 a(7) = 5 + 5 + 17 = 27.
%e A155877 a(8) = 3 + 17 + 17 = 37.
%e A155877 a(9) = 5 + 17 + 17 = 39.
%e A155877 a(10) = 17 + 17 + 17 = 51.
%e A155877 a(11) = 3 + 3 + 257 = 263.
%Y A155877 Cf. A000215, A019434, A050922, A051179, A059919, A063486, A073617, A078303, A078304, A085866.
%K A155877 nonn
%O A155877 1,1
%A A155877 _Jonathan Vos Post_, Jan 29 2009
%E A155877 More terms from _R. J. Mathar_, Feb 06 2009