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A320015 Number of proper divisors of n that are either of the form 6*k+1 or 6*k + 5. 5
0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 1, 1, 2, 2, 1, 2, 1, 2, 1, 1, 2, 2, 3, 1, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 1, 2, 3, 2, 2, 1, 1, 3, 2, 2, 2, 1, 2, 1, 2, 2, 1, 3, 2, 1, 2, 2, 4, 1, 1, 1, 2, 3, 2, 3, 2, 1, 2, 1, 2, 1, 2, 3, 2, 2, 2, 1, 2, 3, 2, 2, 2, 3, 1, 1, 3, 2, 3, 1, 2, 1, 2, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,10

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

FORMULA

a(n) = A320001(n) + A320005(n).

a(n) = A035218(n) - ch15(n), where ch15 is the characteristic function of numbers of the form +-1 mod 6, i.e., ch15(n) = A232991(n-1).

PROG

(PARI) A320015(n) = if(!n, n, sumdiv(n, d, (d<n)&&(d%2)&&(d%3)));

CROSSREFS

Cf. A035218, A232991, A293895, A293896, A320001, A320005.

Sequence in context: A316790 A316789 A319661 * A241918 A276317 A289944

Adjacent sequences:  A320012 A320013 A320014 * A320016 A320017 A320018

KEYWORD

nonn

AUTHOR

Antti Karttunen, Oct 03 2018

STATUS

approved

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Last modified September 29 14:39 EDT 2020. Contains 337432 sequences. (Running on oeis4.)