a(n) = Sum_{d divides n} (-1)^(d + n/d) * d^6.

Terms

a(0) =1a(1) =-65a(2) =730a(3) =-4033a(4) =15626a(5) =-47450a(6) =117650a(7) =-257985a(8) =532171a(9) =-1015690a(10) =1771562a(11) =-2944090a(12) =4826810a(13) =-7647250a(14) =11406980a(15) =-16510913a(16) =24137570a(17) =-34591115a(18) =47045882a(19) =-63019658a(20) =85884500a(21) =-115151530a(22) =148035890a(23) =-188329050a(24) =244156251a(25) =-313742650