An alternating sum of greatest common divisors.

Terms

a(0) =1a(1) =0a(2) =1a(3) =-4a(4) =1a(5) =-8a(6) =1a(7) =-16a(8) =-3a(9) =-16a(10) =1a(11) =-36a(12) =1a(13) =-24a(14) =-15a(15) =-48a(16) =1a(17) =-48a(18) =1a(19) =-68a(20) =-23a(21) =-40a(22) =1a(23) =-112a(24) =-15a(25) =-48a(26) =-27a(27) =-100a(28) =1a(29) =-120