Voozh

A102391

Evil numbers in evil places.

0, 0, 0, 3, 0, 5, 6, 0, 0, 9, 10, 0, 12, 0, 0, 15, 0, 17, 18, 0, 20, 0, 0, 23, 24, 0, 0, 27, 0, 29, 30, 0, 0, 33, 34, 0, 36, 0, 0, 39, 40, 0, 0, 43, 0, 45, 46, 0, 48, 0, 0, 51, 0, 53, 54, 0, 0, 57, 58, 0, 60, 0, 0, 63, 0, 65, 66, 0, 68, 0, 0, 71, 72, 0, 0, 75, 0, 77, 78, 0, 80, 0, 0, 83, 0, 85

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OFFSET

0,4

COMMENTS

Evil numbers A001969(n) appear at positions indexed by the evil numbers, 0 otherwise. A001477(n) = A102391(n) + A102392(n).

LINKS

Table of n, a(n) for n=0..85.

FORMULA

a(n) = if((1+floor(n/2)) (1+(-1)^A000120(n))/2 = 0, 0, n).

a(n) = if((1+floor(n/2)) (1+(-1)^A010060(n))/2 = 0, 0, n).

MATHEMATICA

a[n_] := If[EvenQ @ DigitCount[n, 2, 1], n, 0]; Array[a, 100, 0] (* Amiram Eldar, Aug 02 2020 *)