_M. F. Hasler (Maximilian.Hasler(AT)gmail.com), _, Feb 01 2009

OEIS Server: https://oeis.org/edit/global/893

Least positive integer such that a(n)! starts with n, both written in base 6.

1, 2, 5, 4, 8, 3, 9, 26, 52, 18, 25, 10, 33, 53, 32, 15, 13, 20, 30, 5, 17, 42, 7, 4, 23, 43, 78, 50, 28, 113, 8, 44, 19, 334, 59, 100, 195, 27, 22, 14, 91, 172, 371, 16, 93, 9, 12, 102, 66, 26, 46, 95, 279, 303, 69, 331, 272, 52, 286, 79, 264, 298, 18, 21, 190, 104, 47, 138, 255

1,2

a(3) = 5 since 5!=120 is the least factorial to start with digit "3" when written in base 6. a(8) = 26 since 8 = 12[6] (i.e. written in base 6) and 26! is the smallest factorial to start with digits "12" when written in base 6.

(PARI) A155896(n)={ local( F=1, k=1 ); while( F\1!=n, F*=k++; while( F>=n+1, F/=6)); k}

Cf. A155891--A155894, A018799, A076219.

base,nonn,new

M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Feb 01 2009

approved