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A324534
The smallest common prime factor of sigma(n) and A276086(n), or 1 if no such prime exists.
3
1, 3, 2, 1, 2, 1, 2, 3, 1, 3, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 3, 2, 5, 1, 3, 2, 1, 2, 1, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 1, 2, 3, 2, 3, 2, 1, 1, 3, 2, 7, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 1, 2, 1, 2, 3, 2, 3, 2, 5, 2, 3, 2, 5, 2, 7, 2, 3, 1, 3, 2, 7, 2, 3, 2, 3, 2, 1, 2, 3, 2, 3, 2, 7, 2, 3, 2, 7, 2, 1, 2, 3, 2
OFFSET
1,2
FORMULA
a(n) = A020639(A324644(n)) = A020639(gcd(A000203(n),A276086(n))).
PROG
(PARI)
A276086(n) = { my(i=0, m=1, pr=1, nextpr); while((n>0), i=i+1; nextpr = prime(i)*pr; if((n%nextpr), m*=(prime(i)^((n%nextpr)/pr)); n-=(n%nextpr)); pr=nextpr); m; };
A020639(n) = if(1==n, n, factor(n)[1, 1]);
A324534(n) = A020639(gcd(sigma(n), A276086(n)));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Mar 11 2019
STATUS
approved