A233868 - OEIS

%I #37 Jun 30 2023 22:54:57

%S 1,2,4,7,31,127,511,2047,8191,32767,131071,524287,2097151,8388607,

%T 33554431,134217727,536870911,2147483647,8589934591,34359738367,

%U 137438953471,549755813887,2199023255551,8796093022207,35184372088831

%N Numbers that are not the sum of two evil numbers.

%C 2, 4 together with A083420. - _R. J. Mathar_, Dec 22 2013.

%C Also, numbers that are not the sum of two distinct odious numbers. - _David Radcliffe_, Jul 21 2016

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5, -4).

%F From _Chai Wah Wu_, Aug 02 2020: (Start)

%F a(n) = 5*a(n-1) - 4*a(n-2) for n > 5.

%F G.f.: x*(12*x^4 - 5*x^3 - 2*x^2 - 3*x + 1)/((x - 1)*(4*x - 1)). (End)

%Y Cf. A000069, A000668, A001969, A083420, A175611 (primes that are not the sum of two positive evil numbers).

%K nonn,base,easy

%O 1,2

%A _Juri-Stepan Gerasimov_, Dec 17 2013

%E Terms corrected by _R. J. Mathar_, Dec 22 2013