Ulam's spiral (SSE spoke).

Terms

a(0) =1a(1) =24a(2) =79a(3) =166a(4) =285a(5) =436a(6) =619a(7) =834a(8) =1081a(9) =1360a(10) =1671a(11) =2014a(12) =2389a(13) =2796a(14) =3235a(15) =3706a(16) =4209a(17) =4744a(18) =5311a(19) =5910a(20) =6541a(21) =7204a(22) =7899a(23) =8626a(24) =9385a(25) =10176a(26) =10999a(27) =11854a(28) =12741a(29) =13660