a(n) = (11*n^2 + 11*n - 20)/2.

Terms

a(0) =1a(1) =23a(2) =56a(3) =100a(4) =155a(5) =221a(6) =298a(7) =386a(8) =485a(9) =595a(10) =716a(11) =848a(12) =991a(13) =1145a(14) =1310a(15) =1486a(16) =1673a(17) =1871a(18) =2080a(19) =2300a(20) =2531a(21) =2773a(22) =3026a(23) =3290a(24) =3565a(25) =3851a(26) =4148a(27) =4456a(28) =4775a(29) =5105