OFFSET
1,2
FORMULA
a(p) = p + 2 for p = odd primes (A065091).
EXAMPLE
a(6) = lcm(tau(1), sigma(1)) + lcm(tau(2), sigma(2)) + lcm(tau(3), sigma(3)) + lcm(tau(6), sigma(6)) = lcm(1, 1) + lcm(2, 3) + lcm(2, 4) + lcm(4, 12) = 1 + 6 + 4 + 12 = 23.
MATHEMATICA
a[n_] := DivisorSum[n, LCM[DivisorSigma[0, #], DivisorSigma[1, #]] &]; Array[a, 100] (* Amiram Eldar, May 10 2020 *)
PROG
(Magma) [&+[LCM(#Divisors(d), &+Divisors(d)): d in Divisors(n)]: n in [1..100]]
(PARI) a(n) = sumdiv(n, d, lcm(numdiv(d), sigma(d))); \\ Michel Marcus, May 10 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, May 10 2020
STATUS
approved