Sum_{1<=k<n} gcd(k!,n!/k!).

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =6a(5) =21a(6) =22a(7) =73a(8) =210a(9) =1693a(10) =1694a(11) =2097a(12) =2098a(13) =12997a(14) =21468a(15) =174169a(16) =174170a(17) =1986237a(18) =1986238a(19) =10178833a(20) =16875654a(21) =246551437a(22) =246551438a(23) =2032266537a(24) =3767596738a(25) =45445808989a(26) =260705796192