|
|
A363521
|
|
Product of the divisors d of n such that sqrt(n) < d < n.
|
|
1
|
|
|
1, 1, 1, 1, 1, 3, 1, 4, 1, 5, 1, 24, 1, 7, 5, 8, 1, 54, 1, 50, 7, 11, 1, 576, 1, 13, 9, 98, 1, 900, 1, 128, 11, 17, 7, 1944, 1, 19, 13, 1600, 1, 2058, 1, 242, 135, 23, 1, 36864, 1, 250, 17, 338, 1, 4374, 11, 3136, 19, 29, 1, 1080000, 1, 31, 189, 512, 13, 7986, 1, 578, 23
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,6
|
|
LINKS
|
|
|
FORMULA
|
a(n) = Product_{d|n, sqrt(n) < d < n} d.
|
|
EXAMPLE
|
The divisors of 16 are {1,2,4,8,16} and the product of the divisors d of n such that sqrt(16) = 4 < d < 16 is 8, so a(16) = 8.
The divisors of 30 are {1,2,3,5,6,10,15,30} and the product of the divisors d of n such that sqrt(30) < d < 30 is 6*10*15 = 900, so a(30) = 900.
|
|
MATHEMATICA
|
a[n_] := Product[If[n < d^2 < n^2, d, 1], {d, Divisors[n]}]; Array[a, 100] (* Amiram Eldar, Jun 08 2023 *)
|
|
PROG
|
(PARI) a(n) = vecprod(select(x->((sqrt(n)<x) && (x<n)), divisors(n))); \\ Michel Marcus, Jun 08 2023
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|