Related to population of numbers of form x^2 + y^2.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =11a(5) =19a(6) =34a(7) =63a(8) =117a(9) =218a(10) =411a(11) =780a(12) =1487a(13) =2849a(14) =5477a(15) =10562a(16) =20419a(17) =39563a(18) =76805a(19) =149360a(20) =290896a(21) =567321a(22) =1107775a(23) =2165487a(24) =4237384a(25) =8299283a(26) =16268639a(27) =31915437a(28) =62656158a(29) =123088460