A233868 Numbers that are not the sum of two evil numbers.

1, 2, 4, 7, 31, 127, 511, 2047, 8191, 32767, 131071, 524287, 2097151, 8388607, 33554431, 134217727, 536870911, 2147483647, 8589934591, 34359738367, 137438953471, 549755813887, 2199023255551, 8796093022207, 35184372088831

Offset: 1

Author

Juri-Stepan Gerasimov, Dec 17 2013

Keywords

• nonn
• base
• easy

Comments

2, 4 together with A083420. - R. J. Mathar, Dec 22 2013.

Also, numbers that are not the sum of two distinct odious numbers. - David Radcliffe, Jul 21 2016

Links

• Index entries for linear recurrences with constant coefficients, signature (5, -4).

Crossrefs

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

Formula

From Chai Wah Wu, Aug 02 2020: (Start)

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

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

Extensions

Terms corrected by R. J. Mathar, Dec 22 2013