OFFSET
1,2
COMMENTS
LINKS
Daniel Suteu, Table of n, a(n) for n = 1..10000
FORMULA
a(n) <= n with equality iff n belongs to A319630.
From Antti Karttunen, Dec 29 2019: (Start)
a(A108951(n)) = n.
Many of the formulas given in A329900 apply here as well:
(End)
EXAMPLE
f(21/5) = (2*3) * (2*3*5*7) / (2*3*5) = 42, hence g(42) = 21/5 and a(42) = 21.
MATHEMATICA
Array[#1/GCD[#1, #2] & @@ {#, Apply[Times, Map[If[#1 <= 2, 1, NextPrime[#1, -1]]^#2 & @@ # &, FactorInteger[#]]]} &, 120] (* Michael De Vlieger, Aug 27 2020 *)
PROG
(PARI) a(n) = my (f=factor(n)); numerator(prod(i=1, #f~, my (p=f[i, 1]); (p/if (p>2, precprime(p-1), 1))^f[i, 2]))
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Rémy Sigrist, Sep 25 2018
EXTENSIONS
"Primorial deflation" prefixed to the name by Antti Karttunen, Dec 29 2019
STATUS
approved