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A353361 Number of divisors d of n for which A156552(d) is not a multiple of 3. 4
0, 1, 1, 1, 1, 3, 1, 2, 1, 2, 1, 4, 1, 3, 3, 2, 1, 4, 1, 3, 2, 2, 1, 6, 1, 3, 2, 4, 1, 5, 1, 3, 3, 2, 3, 5, 1, 3, 2, 4, 1, 6, 1, 3, 4, 2, 1, 7, 1, 3, 3, 4, 1, 6, 2, 6, 2, 3, 1, 8, 1, 2, 3, 3, 3, 5, 1, 3, 3, 6, 1, 8, 1, 3, 4, 4, 3, 6, 1, 5, 2, 2, 1, 8, 2, 3, 2, 4, 1, 7, 2, 3, 3, 2, 3, 9, 1, 4, 4, 4, 1, 5, 1, 6, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,6
LINKS
FORMULA
a(n) = Sum_{d|n} (1-A353269(d)).
a(n) = A000005(n) - A353362(n).
a(p) = 1 for all primes p.
a(n) = a(A003961(n)) = a(A348717(n)), for all n >= 1.
PROG
(PARI)
A156552(n) = { my(f = factor(n), p, p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res };
A353269(n) = (!(A156552(n)%3));
A353361(n) = sumdiv(n, d, !A353269(d));
CROSSREFS
Cf. also A353351.
Sequence in context: A271418 A230500 A010281 * A298421 A080131 A319956
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 15 2022
STATUS
approved

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Last modified February 25 00:32 EST 2024. Contains 370308 sequences. (Running on oeis4.)