login
A373493
a(n) = 1 if A059975(n) and A003415(n) are both multiples of 3, otherwise 0, where A059975 is fully additive with a(p) = p-1, and A003415 is the arithmetic derivative.
4
1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1
OFFSET
1
FORMULA
a(n) = [A373378(n) == 0 (mod 3)], where [ ] is the Iverson bracket.
a(n) >= A373491(n).
PROG
(PARI)
A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
A059975(n) = {my(f = factor(n)); sum(i = 1, #f~, f[i, 2]*(f[i, 1] - 1)); };
A373493(n) = (!(A059975(n)%3) && !(A003415(n)%3));
CROSSREFS
Characteristic function of A373494.
Sequence in context: A373588 A373596 A373472 * A014646 A015283 A014548
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jun 10 2024
STATUS
approved