Alternating LCM-sum: a(n) = Sum_{k=1..n} (-1)^(k-1)*lcm(k,n).

Terms

a(0) =1a(1) =0a(2) =0a(3) =8a(4) =-5a(5) =18a(6) =-14a(7) =80a(8) =-9a(9) =100a(10) =-44a(11) =204a(12) =-65a(13) =294a(14) =30a(15) =672a(16) =-119a(17) =540a(18) =-152a(19) =1040a(20) =63a(21) =1210a(22) =-230a(23) =1752a(24) =-75a(25) =2028a(26) =-54a(27) =2996a(28) =-377a(29) =2190