A066278 Least solution to cototient(x) = n!, where cototient(x) = x-phi(x).

2, 4, 10, 36, 168, 1008, 7056, 56448, 470400, 4704000, 51528960, 618347520, 7740902400, 108372633600

Offset: 1

Author

Labos Elemer, Dec 10 2001

Keywords

• nonn
• more

Comments

a(15) <= 1625589504000. a(16) <= 26009432064000. a(17) <= 442160345088000. [Donovan Johnson, Feb 05 2010]

Examples

			Solutions to x-Phi[x]=720 are {1008,1424,1432,1436,1438} of which the smallest is a(6)=1008.
		

Crossrefs

Cf. A000010, A051953, A000142, A055487.

Programs

PARI

a(n) = my(x=1); while(x-eulerphi(x) != n!, x++); x; \\ Michel Marcus, Aug 24 2019

Formula

a(n) = Min{x; x-A000010(x)=n!} = Min{A051953(x)=A000142(n)}.

Extensions

a(12)-a(14) from Donovan Johnson, Feb 05 2010