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A322359
Least common multiple of product (p-1) and product (p+1), where p ranges over distinct prime divisors of n.
5
1, 3, 4, 3, 12, 12, 24, 3, 4, 36, 60, 12, 84, 24, 24, 3, 144, 12, 180, 36, 96, 180, 264, 12, 12, 84, 4, 24, 420, 72, 480, 3, 240, 432, 48, 12, 684, 180, 168, 36, 840, 96, 924, 180, 24, 792, 1104, 12, 24, 36, 288, 84, 1404, 12, 360, 24, 720, 1260, 1740, 72, 1860, 480, 96, 3, 336, 720, 2244, 432, 1056, 144, 2520, 12
OFFSET
1,2
FORMULA
a(n) = lcm(A048250(n), A173557(n)).
a(n) = A322360(n)/A066086(n).
MATHEMATICA
a[n_] := If[n == 1, 1, Module[{f=FactorInteger[n]}, LCM[Times@@((#-1)& @@@ f), Times@@((#+1)& @@@ f)]]]; Array[a, 100] (* Amiram Eldar, Dec 05 2018 *)
PROG
(PARI)
A048250(n) = factorback(apply(p -> p+1, factor(n)[, 1]));
A173557(n) = factorback(apply(p -> p-1, factor(n)[, 1]));
A322359(n) = lcm(A048250(n), A173557(n));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Dec 04 2018
STATUS
approved