Sum of numbers under a triangle on a spiral staircase of width 10.

Terms

a(0) =11a(1) =44a(2) =110a(3) =220a(4) =385a(5) =616a(6) =924a(7) =1320a(8) =1815a(9) =2420a(10) =3146a(11) =4004a(12) =5005a(13) =6160a(14) =7480a(15) =8976a(16) =10659a(17) =12540a(18) =14630a(19) =16940a(20) =19481a(21) =22264a(22) =25300a(23) =28600a(24) =32175a(25) =36036a(26) =40194a(27) =44660a(28) =49445a(29) =54560