OFFSET
1,2
FORMULA
a(p) = p^2 + p for p = primes (A000040).
EXAMPLE
a(6) = lcm(1, sigma(1)) * lcm(2, sigma(2)) * lcm(3, sigma(3)) * lcm(6, sigma(6)) = lcm(1, 1) * lcm(2, 3) * lcm(3, 4) * lcm(6, 12) = 1 * 6 * 12 * 12 = 864.
MATHEMATICA
a[n_] := Product[LCM[d, DivisorSigma[1, d]], {d, Divisors[n]}]; Array[a, 35] (* Amiram Eldar, Jun 27 2020 *)
PROG
(Magma) [&*[LCM(d, &+Divisors(d)): d in Divisors(n)]: n in [1..100]]
(PARI) a(n) = my(d=divisors(n)); prod(k=1, #d, lcm(d[k], sigma(d[k]))); \\ Michel Marcus, Jun 27 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jun 26 2020
STATUS
approved