a(n) = lcm(1,2,...,n) * Sum_{k=1..n} (2^(k-1) - 1) / k.

Terms

a(0) =0a(1) =1a(2) =9a(3) =39a(4) =375a(5) =685a(6) =8575a(7) =30485a(8) =162855a(9) =291627a(10) =5785857a(11) =10514427a(12) =250200951a(13) =461037291a(14) =854622483a(15) =3185234481a(16) =101381371377a(17) =190598779657