a(n) = Sum_{k=1..n} (k/gcd(n, k))^4.

Terms

a(0) =1a(1) =2a(2) =18a(3) =84a(4) =355a(5) =645a(6) =2276a(7) =3192a(8) =7413a(9) =9400a(10) =25334a(11) =18395a(12) =60711a(13) =52747a(14) =88760a(15) =106688a(16) =243849a(17) =137790a(18) =432346a(19) =275570a(20) =499867a(21) =522513a(22) =1151404a(23) =561415a(24) =1542125a(25) =1214436a(26) =1907502a(27) =1569673a(28) =3756719a(29) =1344999