OFFSET
1,2
FORMULA
a(p) = p *(p + 1) for p = primes (A000040).
EXAMPLE
a(6) = lcm(6, tau(6), sigma(6)) = lcm(6, 4, 12) = 12.
MATHEMATICA
a[n_] := LCM @@ {n, DivisorSigma[0, n], DivisorSigma[1, n]}; Array[a, 50] (* Amiram Eldar, Nov 03 2020 *)
PROG
(Magma) [LCM([n, #Divisors(n), &+Divisors(n)]): n in [1..100]]
(PARI) a(n) = my(f=factor(n)); lcm([n, sigma(f), numdiv(f)]); \\ Michel Marcus, Nov 03 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Nov 02 2020
STATUS
approved