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A155895
Least positive integer such that a(n)! starts with n, both written in base 5.
1
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
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
KEYWORD
base,nonn
AUTHOR
M. F. Hasler, Feb 01 2009
STATUS
approved