OFFSET
0
LINKS
FORMULA
a(n) = [A003415(n) == 0 (mod 3)], where [ ] is the Iverson bracket.
From Antti Karttunen, Jun 13 2024: (Start)
a(n) >= A369643(n).
a(n) >= A373143(n).
a(n) >= A370118(n).
(End)
PROG
(PARI)
A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
(PARI) A359430(n) = if(!n, 1, if(!(n%3), !(n%9), my(f = factor(n), m1=0, m2=0); for(i=1, #f~, if(1==(f[i, 1]%3), m1 += f[i, 2], m2 += f[i, 2])); 0==((m1-m2)%3))); \\ Antti Karttunen, Jun 13 2024
CROSSREFS
Characteristic function of A327863.
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 02 2023
STATUS
approved