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A323068
Number of divisors d of n such that A049820(d) > 0 and A049820(d) is also a divisor of n.
3
0, 0, 1, 1, 0, 2, 0, 2, 1, 0, 0, 4, 0, 0, 2, 2, 0, 3, 0, 1, 1, 0, 0, 5, 0, 0, 1, 1, 0, 4, 0, 2, 1, 0, 1, 6, 0, 0, 1, 2, 0, 2, 0, 1, 2, 0, 0, 6, 0, 0, 1, 1, 0, 3, 0, 2, 1, 0, 0, 6, 0, 0, 1, 2, 0, 2, 0, 1, 1, 2, 0, 7, 0, 0, 2, 1, 0, 2, 0, 2, 1, 0, 0, 4, 0, 0, 1, 2, 0, 5, 0, 1, 1, 0, 0, 6, 0, 0, 2, 1, 0, 2, 0, 2, 3
OFFSET
1,6
COMMENTS
Records 0, 1, 2, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 19, 20, 22, 27, 30, ... occur at n = 1, 3, 6, 12, 24, 36, 72, 144, 240, 360, 720, 1440, 1680, 2640, 3360, 5040, 7920, 10080, 30240, 55440, ...
LINKS
FORMULA
Sum_{d|n} [A049820(d) > 0 and A049820(d)|n], where [ ] is the Iverson bracket.
a(n) >= A323069(n) => A322358(n).
PROG
(PARI) A323068(n) = sumdiv(n, d, my(t=(d-numdiv(d))); ((t>0)&&!(n%t)));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 05 2019
STATUS
approved