OFFSET
1,3
LINKS
FORMULA
Sum_{k=1..n} a(k) ~ c * n^3, where c = (1/3) * Product_{p prime} (1 - (3*p^2 - 4*p + 2)/(p*(p^3 - p + 1))) = 0.1161464566... . - Amiram Eldar, Nov 19 2022
MAPLE
a:= n-> mul((i[1]-1)^(i[2]+1), i=ifactors(n)[2]):
seq(a(n), n=1..65); # Alois P. Heinz, Feb 11 2022
MATHEMATICA
f[p_, e_] := (p - 1)^(e + 1); a[1] = 1; a[n_] := Times @@ (f @@@ FactorInteger[n]); Table[a[n], {n, 1, 65}]
PROG
(PARI) a(n) = my(f=factor(n)); for (k=1, #f~, f[k, 1]--; f[k, 2]++); factorback(f); \\ Michel Marcus, Feb 11 2022
CROSSREFS
KEYWORD
nonn,mult
AUTHOR
Ilya Gutkovskiy, Feb 11 2022
STATUS
approved