Sum of totient function: a(n) = Sum_{k=1..n} phi(k), cf. A000010.

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =6a(5) =10a(6) =12a(7) =18a(8) =22a(9) =28a(10) =32a(11) =42a(12) =46a(13) =58a(14) =64a(15) =72a(16) =80a(17) =96a(18) =102a(19) =120a(20) =128a(21) =140a(22) =150a(23) =172a(24) =180a(25) =200a(26) =212a(27) =230a(28) =242a(29) =270