A068158 a(n) = floor(n!/R(n)!), where R(n) = digit reversal of n (A004086).

1, 1, 1, 1, 1, 1, 1, 1, 1, 3628800, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1216451004088320000, 106661318400, 1, 0, 0, 0, 0, 0, 0, 0, 44208809968698509772718080000000, 1320509264105545113600000, 10178348544000, 1, 0, 0, 0, 0, 0, 0

Offset: 1

Author

Amarnath Murthy, Feb 24 2002

Keywords

• base
• easy
• nonn

Comments

If n < R(n) then a(n) = 0.

If n = R(n) then n is a palindrome and a(n) = 1.

If n > R(n) then n!/R(n)! is an integer.

Examples

			a(21) = 21! / 12! = 51090942171709440000/479001600 = 106661318400.
		

Crossrefs

Cf. A004086.

Programs

PARI

a(n) = n!\fromdigits(Vecrev(digits(n)))!; \\ Michel Marcus, Aug 19 2024