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a(n) = Sum_{r < n, gcd(r,n)=1} n!/r!.
2

%I #7 Sep 03 2017 03:30:49

%S 1,2,9,28,205,726,8659,47384,562545,4234330,68588311,483088332,

%T 10699776685,102434734598,2016289908585,24588487650736,

%U 611171244308689,6456997293606738,209020565553571999,2838875160624256460

%N a(n) = Sum_{r < n, gcd(r,n)=1} n!/r!.

%e a(6) = 6!(1/1! + 1/5!) = 726.

%p a:=proc(n) local s,r: s:=0: for r from 1 to n do if gcd(r,n)=1 then s:=s+1/r! else s:=s: fi: od: n!*s end: seq(a(n),n=1..23); # _Emeric Deutsch_, Jul 25 2005

%Y Cf. A038048, A110276, A110373, A110374.

%K easy,nonn

%O 1,2

%A _Amarnath Murthy_, Jul 24 2005

%E More terms from _Emeric Deutsch_, Jul 25 2005