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A159481 Number of evil numbers <= n, see A001969. 7
1, 1, 1, 2, 2, 3, 4, 4, 4, 5, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 11, 11, 11, 12, 13, 13, 13, 14, 14, 15, 16, 16, 16, 17, 18, 18, 19, 19, 19, 20, 21, 21, 21, 22, 22, 23, 24, 24, 25, 25, 25, 26, 26, 27, 28, 28, 28, 29, 30, 30, 31, 31, 31, 32, 32, 33, 34, 34, 35, 35, 35, 36, 37, 37, 37 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

a(n) = n + 1 - A115384(n);

n/a(n)-->1/2.

LINKS

R. Zumkeller, Table of n, a(n) for n = 0..10000

FORMULA

a(n) = Sum_{k=0..n} A010059(k).

a(n) = floor(n/2) - (1 + (-1)^n)*(1 - (-1)^A000120(n))/4 + 1. - Vladimir Shevelev, May 27 2009

G.f.: (1/(1 - x)^2 + Product_{k>=1} (1 - x^(2^k)))/2. - Ilya Gutkovskiy, Apr 03 2019

EXAMPLE

a(10) = #{0,11,101,110,1001,1010} = #{0,3,5,6,9,10} = 6.

MATHEMATICA

Accumulate[Table[If[EvenQ[DigitCount[n, 2, 1]], 1, 0], {n, 0, 80}]] (* Harvey P. Dale, Mar 19 2018 *)

PROG

(PARI) a(n)=n\2+(n%2&&hammingweight(n)%2) \\ Charles R Greathouse IV, Mar 22 2013

CROSSREFS

Cf. A000120, A001969, A010059, A115384.

Sequence in context: A092038 A269990 A324473 * A194206 A307482 A046699

Adjacent sequences:  A159478 A159479 A159480 * A159482 A159483 A159484

KEYWORD

nonn,easy

AUTHOR

Reinhard Zumkeller, Apr 16 2009

STATUS

approved

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Last modified June 20 00:47 EDT 2019. Contains 324223 sequences. (Running on oeis4.)