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

1,10

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.

Links

Table of n, a(n) for n=1..39.

Example

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

Prog

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

Crossrefs

Cf. A004086.

Sequence in context: A118813 A127229 A269128 * A011521 A321846 A226889

Adjacent sequences: A068155 A068156 A068157 * A068159 A068160 A068161

Keyword

base,easy,nonn

Author

Amarnath Murthy, Feb 24 2002

Status

approved