A378056 a(n) = gcd(A057643(n), A084190(n)) = gcd(lcm{d+1 : d|n}, lcm{d-1 : d > 1 and d|n}).
1, 1, 2, 3, 2, 2, 2, 3, 4, 6, 2, 30, 2, 6, 4, 15, 2, 20, 2, 6, 4, 6, 2, 210, 6, 6, 4, 6, 2, 84, 2, 15, 4, 6, 12, 420, 2, 6, 4, 126, 2, 60, 2, 30, 8, 6, 2, 210, 8, 6, 4, 30, 2, 20, 12, 90, 4, 6, 2, 4620, 2, 6, 40, 45, 6, 84, 2, 6, 4, 36, 2, 420, 2, 6, 24, 30, 12
Offset: 1
Keywords
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
-
Mathematica
a[n_] := Module[{d = Divisors[n]}, GCD[LCM @@ (d + 1), LCM @@ (Rest @ d - 1)]]; a[1] = 1; Array[a, 100] -
PARI
a(n) = {my(d = divisors(n)); gcd(lcm(apply(x->x+1, d)), lcm(apply(x -> if(x > 1, x-1, x), d)));}