

A269225


Smallest k such that k! > 2^n.


1



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OFFSET

0,1


LINKS



EXAMPLE

a(7) = 6 because 6! = 720 > 2^7 = 128, but 5! = 120 < 128.


MATHEMATICA

a[n_] := Block[{v=2^n, k=1}, While[++k! <= v]; k]; Array[a, 93, 0] (* Giovanni Resta, Jul 11 2016 *)


PROG

(Python)
def a269225():
...k = 1
...f = 1
...p = 1
...n = 0
...while True:
......while f<=p:
.........k += 1
.........f *= k
......yield k
......p *= 2
......n += 1
(PARI) a(n)=localprec(19); my(t=log(2)*n, x=ceil(solve(k=1, n/2+5, lngamma(k+1)t))); while(x!<=2^n, x++); x \\ Charles R Greathouse IV, Jul 12 2016


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



STATUS

approved



