a(n) = Sum_{1 <= x_1, x_2 <= n} ( n/gcd(x_1, x_2, n) )^3.

Terms

a(0) =1a(1) =25a(2) =217a(3) =793a(4) =3001a(5) =5425a(6) =16465a(7) =25369a(8) =52705a(9) =75025a(10) =159721a(11) =172081a(12) =369097a(13) =411625a(14) =651217a(15) =811801a(16) =1414945a(17) =1317625a(18) =2469241a(19) =2379793a(20) =3572905a(21) =3993025a(22) =6424177a(23) =5505073a(24) =9378001a(25) =9227425a(26) =12807289a(27) =13056745a(28) =20486761a(29) =16280425