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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 September 24 06:13 EDT 2021. Contains 347623 sequences. (Running on oeis4.)