a(n) = (-6*n^7 + 154*n^6 - 1533*n^5 + 7525*n^4 - 18879*n^3 + 22561*n^2 - 7302*n + 2520)/2520.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =6a(5) =8a(6) =12a(7) =24a(8) =39a(9) =-2a(10) =-295a(11) =-1308a(12) =-3980a(13) =-9996a(14) =-22150a(15) =-44808a(16) =-84483a(17) =-150534a(18) =-256001a(19) =-418588a(20) =-661806a(21) =-1016288a(22) =-1521288a(23) =-2226376a(24) =-3193341a(25) =-4498314a(26) =-6234123a(27) =-8512892a(28) =-11468896a(29) =-15261684