Integer part of ((4th elementary symmetric function of 1,2,...,n)/(1+2+...+n)).

Terms

a(0) =0a(1) =0a(2) =0a(3) =2a(4) =18a(5) =77a(6) =241a(7) =623a(8) =1406a(9) =2868a(10) =5415a(11) =9608a(12) =16203a(13) =26188a(14) =40830a(15) =61720a(16) =90827a(17) =130548a(18) =183773a(19) =253942a(20) =345116a(21) =462042a(22) =610231a(23) =796034a(24) =1026724a(25) =1310578a(26) =1656969a(27) =2076457a(28) =2580887a(29) =3183486