A136766 a(n) = leading digit of n! in base 16.

1, 1, 2, 6, 1, 7, 2, 1, 9, 5, 3, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 5, 8, 12, 1, 2, 3, 6, 13, 1, 3, 6, 13, 1, 4, 9, 1, 3, 8, 1, 3, 10, 1, 4, 14, 2, 7, 1, 4, 14, 2, 9, 2, 7, 1, 5, 1, 4, 1, 4, 1, 3, 15, 4, 1, 4, 1, 5, 1, 6, 1, 7, 2, 10, 3, 15, 4, 1, 7, 2, 11, 3, 1, 6, 2, 11, 4, 1, 7, 2, 1, 5, 2, 12, 4, 1, 11

Offset: 0

Author

Carl R. White, Jan 21 2008

Keywords

• nonn
• easy
• base

Examples

			For n=5, 5! = 5*4*3*2*1 = 120 in base 10, which is 78 in hexadecimal (7*16 + 8*1), so a(5) = 7. - _Michael B. Porter_, Sep 20 2016
		

Links

• David A. Corneth, Table of n, a(n) for n = 0..9999 (first 1001 terms from Robert G. Wilson v)

Crossrefs

Cf. A000142, A136702, A136754, A136755, A136756, A136757, A136758, A136759, A136760, A008905, A136761, A136762, A136763, A136764, A136765.

Programs

Mathematica

Array[ IntegerDigits[#!, 16][[1]] &, 1001, 0] (* Robert G. Wilson v, Sep 20 2016 *)
Table[Floor[#/16^Floor@ Log[16, #]] &[n!], {n, 0, 98}] (* Michael De Vlieger, Sep 20 2016 *)

PARI

a(n) = digits(n!, 16)[1]; \\ Michel Marcus, Jan 27 2015