a(n) = (n^4 + n^2 + 2*n)/4.

Terms

a(0) =0a(1) =1a(2) =6a(3) =24a(4) =70a(5) =165a(6) =336a(7) =616a(8) =1044a(9) =1665a(10) =2530a(11) =3696a(12) =5226a(13) =7189a(14) =9660a(15) =12720a(16) =16456a(17) =20961a(18) =26334a(19) =32680a(20) =40110a(21) =48741a(22) =58696a(23) =70104a(24) =83100a(25) =97825a(26) =114426a(27) =133056a(28) =153874a(29) =177045