Ulam's spiral (SSW spoke).

Terms

a(0) =1a(1) =22a(2) =75a(3) =160a(4) =277a(5) =426a(6) =607a(7) =820a(8) =1065a(9) =1342a(10) =1651a(11) =1992a(12) =2365a(13) =2770a(14) =3207a(15) =3676a(16) =4177a(17) =4710a(18) =5275a(19) =5872a(20) =6501a(21) =7162a(22) =7855a(23) =8580a(24) =9337a(25) =10126a(26) =10947a(27) =11800a(28) =12685a(29) =13602