OFFSET
1,1
COMMENTS
The asymptotic density of this sequence is log_10(6/5) = 0.079181... (Kunoff, 1987). - Amiram Eldar, Jul 17 2020
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10000
Sharon Kunoff, N! has the first digit property, The Fibonacci Quarterly, Vol. 25, No. 4 (1987), pp. 365-367.
FORMULA
A008905(a(n)) = 5. - Amiram Eldar, Jul 17 2020
EXAMPLE
7 is a term since 7! = 5040 has the initial digit 5.
MAPLE
filter:= proc(t) local tf;
tf:= t!;
floor(tf/10^ilog10(tf)) = 5
end proc:
select(filter, [$1..1000]); # Robert Israel, Feb 07 2017
MATHEMATICA
Select[ Range[ 850 ], IntegerDigits[ #! ] [[1]] == 5 & ]
PROG
(PARI) isok(n) = digits(n!)[1] == 5; \\ Michel Marcus, Feb 08 2017
CROSSREFS
KEYWORD
nonn,base
AUTHOR
STATUS
approved