a(n) = 781250*n^2 - 1107500*n + 392499.

Terms

a(0) =66249a(1) =1302499a(2) =4101249a(3) =8462499a(4) =14386249a(5) =21872499a(6) =30921249a(7) =41532499a(8) =53706249a(9) =67442499a(10) =82741249a(11) =99602499a(12) =118026249a(13) =138012499a(14) =159561249a(15) =182672499a(16) =207346249a(17) =233582499a(18) =261381249a(19) =290742499a(20) =321666249a(21) =354152499