A155895 Least positive integer such that a(n)! starts with n, both written in base 5.

1, 2, 17, 4, 6, 3, 29, 7, 10, 19, 31, 8, 18, 14, 37, 61, 81, 17, 33, 11, 63, 94, 9, 4, 13, 24, 16, 6, 27, 22, 52, 152, 28, 21, 143, 45, 35, 29, 67, 7, 62, 15, 247, 181, 193, 10, 105, 48, 12, 97, 19, 167, 36, 72, 146, 75, 31, 391, 69, 40, 186, 486, 133, 8, 57, 46, 18, 103, 115

Offset

1,2

Links

Table of n, a(n) for n=1..69.

Example

a(3) = 17 since 17! is the least factorial to start with digit "3" when written in base 5. a(5) = 6 since 5 = 10[5] (i.e. written in base 5) and 6! = 720 = 625 + 75 + 20 = 10340[5] is the smallest factorial to start with digits "10" when written in base 5.

Prog

(PARI) A155895(n)={ local( F=1, k=1 ); while( F\1!=n, F*=k++; while( F>=n+1, F/=5)); k}

Crossrefs

Cf. A155891--A155894, A018799, A076219.

Sequence in context: A199295 A162623 A165234 * A293179 A144212 A186683

Adjacent sequences: A155892 A155893 A155894 * A155896 A155897 A155898

Keyword

base,nonn

Author

M. F. Hasler, Feb 01 2009

Status

approved