A155892 Least positive integer such that a(n)! starts with n, both written in base 3.

1, 2, 12, 5, 13, 3, 19, 4, 31, 18, 12, 21, 5, 33, 17, 13, 34, 8, 38, 7, 19, 92, 24, 4, 11, 6, 46, 39, 31, 22, 18, 77, 12, 55, 32, 75, 21, 52, 74, 5, 15, 33, 61, 122, 166, 17, 47, 13, 65, 54, 49, 148, 34, 71, 8, 117, 107, 60, 38, 51, 10, 7, 111, 25, 19, 92, 123, 128, 29, 24, 56, 99

Offset: 1

Author

M. F. Hasler, Feb 01 2009

Keywords

• base
• nonn

Examples

			a(4) = 5 since 4 = 11[3] (i.e. written in base 2) and 5! = 11110[3] is the least factorial to have 11 as most significant digits in base 3.
		

Crossrefs

Cf. A155891, A018799, A076219.

Programs

PARI

A155892(n)={ local( F=1,k=1 ); while( F\1!=n, F*=k++; while( F>=n+1, F/=3 )); k}