a(n) = Sum_{k=1..n} binomial(n,k) * gcd(k,n).

Terms

a(0) =1a(1) =4a(2) =9a(3) =24a(4) =35a(5) =138a(6) =133a(7) =528a(8) =855a(9) =2550a(10) =2057a(11) =12708a(12) =8203a(13) =45178a(14) =78645a(15) =182816a(16) =131087a(17) =933966a(18) =524305a(19) =3698220a(20) =4890627a(21) =13345794a(22) =8388629a(23) =67390440a(24) =60129575a(25) =225470518a(26) =279938133a(27) =1032462228a(28) =536870939a(29) =5018059170