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A230120
a(n) is the number of evil integers (A001969) not exceeding n and respectively prime to n.
2
0, 0, 0, 1, 1, 1, 3, 2, 1, 2, 5, 1, 6, 3, 0, 4, 7, 2, 9, 3, 4, 5, 10, 3, 8, 6, 5, 7, 13, 3, 15, 8, 6, 8, 12, 4, 18, 9, 7, 8, 20, 4, 20, 10, 5, 11, 23, 5, 24, 9, 8, 12, 25, 6, 19, 14, 11, 14, 29, 5, 30, 15, 12, 16, 22, 7, 33, 15, 12, 12, 34, 8, 36, 18, 10, 18
OFFSET
1,7
COMMENTS
See comment in A230070, taking into account the equality a(n) = phi(n) - A230070(n), where phi(n) is Euler totient function (A000010).
LINKS
FORMULA
For odd evil prime p (A027699), a(p) = (p-3)/2; for odd odious prime p (A027697), a(p) = (p-1)/2.
MATHEMATICA
evils=Select[Range[rng=100], EvenQ[DigitCount[#, 2][[1]]]&]; tmp=0; Table[Count[Map[CoprimeQ[n, #]&, Take[evils, tmp=NestWhile[#+1&, tmp+1, evils[[#]]<n && !(Length[evils]<=tmp+1)&]-1]], True], {n, rng}]
PROG
(PARI) a(n) = sum(k = 1, n, gcd(k, n) == 1 && !(hammingweight(k) % 2)); \\ Amiram Eldar, Nov 10 2024
CROSSREFS
KEYWORD
nonn,base,changed
AUTHOR
Vladimir Shevelev, Oct 10 2013
STATUS
approved