OFFSET
1,2
COMMENTS
See A319522 for a similar sequence.
The function n -> (a(n), A319522(n)) establishes a bijection from N to N x N (where N = A000027); see A319523 for the corresponding inverse function.
This sequence has similarities with A059905: here we keep one p-adic valuation out of two, there we keep one binary digit out of two.
FORMULA
EXAMPLE
a(42) = a(prime(1)) * a(prime(2)) * a(prime(4)) = prime(1) * 1 * 1 = 2.
PROG
(PARI) a(n) = my (f=factor(n)); prod(i=1, #f~, my (pi=primepi(f[i, 1])); if (pi%2==1, prime(1+pi\2)^f[i, 2], 1))
CROSSREFS
KEYWORD
nonn,mult
AUTHOR
Rémy Sigrist, Sep 22 2018
STATUS
approved