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A342673
a(n) = gcd(n, sigma(A003961(n))), where A003961 is fully multiplicative with a(prime(k)) = prime(k+1), and sigma is the sum of divisors of n.
3
1, 2, 3, 1, 1, 6, 1, 8, 1, 2, 1, 6, 1, 2, 3, 1, 1, 2, 1, 4, 3, 2, 1, 24, 1, 2, 3, 4, 1, 6, 1, 4, 3, 2, 1, 1, 1, 2, 3, 40, 1, 6, 1, 2, 1, 2, 1, 6, 7, 2, 3, 26, 1, 6, 1, 8, 3, 2, 1, 12, 1, 2, 3, 1, 1, 6, 1, 4, 3, 2, 1, 8, 1, 2, 3, 4, 7, 6, 1, 8, 1, 2, 1, 12, 5, 2, 3, 8, 1, 2, 1, 2, 3, 2, 1, 24, 1, 14, 1, 1, 1, 6, 1, 8, 3
OFFSET
1,2
FORMULA
a(n) = gcd(n, A003973(n)) = gcd(n, A000203(A003961(n))).
PROG
(PARI)
A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A342673(n) = gcd(n, sigma(A003961(n)));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Mar 20 2021
STATUS
approved