a(n) = n*(21*n-1)/2.

Terms

a(0) =0a(1) =10a(2) =41a(3) =93a(4) =166a(5) =260a(6) =375a(7) =511a(8) =668a(9) =846a(10) =1045a(11) =1265a(12) =1506a(13) =1768a(14) =2051a(15) =2355a(16) =2680a(17) =3026a(18) =3393a(19) =3781a(20) =4190a(21) =4620a(22) =5071a(23) =5543a(24) =6036a(25) =6550a(26) =7085a(27) =7641a(28) =8218a(29) =8816