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A066278
Least solution to cototient(x) = n!, where cototient(x) = x-phi(x).
0
2, 4, 10, 36, 168, 1008, 7056, 56448, 470400, 4704000, 51528960, 618347520, 7740902400, 108372633600
OFFSET
1,1
COMMENTS
a(15) <= 1625589504000. a(16) <= 26009432064000. a(17) <= 442160345088000. [Donovan Johnson, Feb 05 2010]
FORMULA
a(n) = Min{x; x-A000010(x)=n!} = Min{A051953(x)=A000142(n)}.
EXAMPLE
Solutions to x-Phi[x]=720 are {1008,1424,1432,1436,1438} of which the smallest is a(6)=1008.
PROG
(PARI) a(n) = my(x=1); while(x-eulerphi(x) != n!, x++); x; \\ Michel Marcus, Aug 24 2019
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Labos Elemer, Dec 10 2001
EXTENSIONS
a(12)-a(14) from Donovan Johnson, Feb 05 2010
STATUS
approved