a(n) = Sum_{k = n..2*n+1} k^2.

Terms

a(0) =1a(1) =14a(2) =54a(3) =135a(4) =271a(5) =476a(6) =764a(7) =1149a(8) =1645a(9) =2266a(10) =3026a(11) =3939a(12) =5019a(13) =6280a(14) =7736a(15) =9401a(16) =11289a(17) =13414a(18) =15790a(19) =18431a(20) =21351a(21) =24564a(22) =28084a(23) =31925a(24) =36101a(25) =40626a(26) =45514a(27) =50779a(28) =56435a(29) =62496