a(n) = M(10^n), where M(n) is Mertens's function.

Terms

a(0) =1a(1) =-1a(2) =1a(3) =2a(4) =-23a(5) =-48a(6) =212a(7) =1037a(8) =1928a(9) =-222a(10) =-33722a(11) =-87856a(12) =62366a(13) =599582a(14) =-875575a(15) =-3216373a(16) =-3195437a(17) =-21830254a(18) =-46758740a(19) =899990187a(20) =461113106a(21) =-3395895277a(22) =-2061910120a(23) =62467771689