Ulam's spiral (WSW spoke).

Terms

a(0) =1a(1) =20a(2) =71a(3) =154a(4) =269a(5) =416a(6) =595a(7) =806a(8) =1049a(9) =1324a(10) =1631a(11) =1970a(12) =2341a(13) =2744a(14) =3179a(15) =3646a(16) =4145a(17) =4676a(18) =5239a(19) =5834a(20) =6461a(21) =7120a(22) =7811a(23) =8534a(24) =9289a(25) =10076a(26) =10895a(27) =11746a(28) =12629a(29) =13544