OFFSET
0,4
COMMENTS
If there are no odd perfect numbers, then all n for which a(n) is 0 are given by sequence A324200.
LINKS
Antti Karttunen, Table of n, a(n) for n = 0..16384
Antti Karttunen, Data supplement: n, a(n) computed for n = 0..65537
FORMULA
PROG
(PARI)
A163511(n) = if(!n, 1, my(p=2, t=1); while(n>1, if(!(n%2), (t*=p), p=nextprime(1+p)); n >>= 1); (t*p));
A033879(n) = (2*n-sigma(n));
(PARI)
A324184(n) = if(!n, 1, my(p=2, mp=p*p, m=1); while(n>1, if(n%2, p=nextprime(1+p); mp = p*p, if((2==n)||!(n%4), mp *= p, m *= (mp-1)/(p-1))); n >>= 1); (m*(mp-1)/(p-1)));
CROSSREFS
KEYWORD
sign,look
AUTHOR
Antti Karttunen, Feb 17 2019
STATUS
approved