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 A233868 #37 Jun 30 2023 22:54:57 %S A233868 1,2,4,7,31,127,511,2047,8191,32767,131071,524287,2097151,8388607, %T A233868 33554431,134217727,536870911,2147483647,8589934591,34359738367, %U A233868 137438953471,549755813887,2199023255551,8796093022207,35184372088831 %N A233868 Numbers that are not the sum of two evil numbers. %C A233868 2, 4 together with A083420. - _R. J. Mathar_, Dec 22 2013. %C A233868 Also, numbers that are not the sum of two distinct odious numbers. - _David Radcliffe_, Jul 21 2016 %H A233868 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5, -4). %F A233868 From _Chai Wah Wu_, Aug 02 2020: (Start) %F A233868 a(n) = 5*a(n-1) - 4*a(n-2) for n > 5. %F A233868 G.f.: x*(12*x^4 - 5*x^3 - 2*x^2 - 3*x + 1)/((x - 1)*(4*x - 1)). (End) %Y A233868 Cf. A000069, A000668, A001969, A083420, A175611 (primes that are not the sum of two positive evil numbers). %K A233868 nonn,base,easy %O A233868 1,2 %A A233868 _Juri-Stepan Gerasimov_, Dec 17 2013 %E A233868 Terms corrected by _R. J. Mathar_, Dec 22 2013