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Smallest factorial containing exactly n 1's.
2

%I #9 Sep 01 2020 08:43:13

%S 1,87178291200,121645100408832000,15511210043330985984000000,

%T 263130836933693530167218012160000000,

%U 815915283247897734345611269596115894272000000000

%N Smallest factorial containing exactly n 1's.

%H Amiram Eldar, <a href="/A072295/b072295.txt">Table of n, a(n) for n = 1..83</a>

%F a(n) = A000142(A072124(n)). - _Amiram Eldar_, Sep 01 2020

%e a(2) = 87178291200 since 87178291200 is the smallest factorial containing exactly two 1's.

%t With[{fctrs=Range[100]!},Table[First[Select[fctrs,DigitCount[#,10,1] == n&]],{n,10}]] (* _Harvey P. Dale_, Sep 29 2011 *)

%Y Cf. A000142, A072124.

%K base,nonn

%O 1,2

%A _Shyam Sunder Gupta_, Jul 30 2002