Ulam's spiral (ENE spoke).

Terms

a(0) =1a(1) =12a(2) =55a(3) =130a(4) =237a(5) =376a(6) =547a(7) =750a(8) =985a(9) =1252a(10) =1551a(11) =1882a(12) =2245a(13) =2640a(14) =3067a(15) =3526a(16) =4017a(17) =4540a(18) =5095a(19) =5682a(20) =6301a(21) =6952a(22) =7635a(23) =8350a(24) =9097a(25) =9876a(26) =10687a(27) =11530a(28) =12405a(29) =13312