a(n) = Sum_{k=0..n} phi(k^2 + 1), where phi is the Euler totient function (A000010).

Terms

a(0) =1a(1) =2a(2) =6a(3) =10a(4) =26a(5) =38a(6) =74a(7) =94a(8) =142a(9) =182a(10) =282a(11) =342a(12) =454a(13) =518a(14) =714a(15) =826a(16) =1082a(17) =1194a(18) =1434a(19) =1614a(20) =2014a(21) =2206a(22) =2590a(23) =2798a(24) =3374a(25) =3686a(26) =4362a(27) =4650a(28) =5274a(29) =5694