a(n) = (n/2) * Sum_{k=0..n} binomial(n,k)/gcd(n,k).

Terms

a(0) =1a(1) =3a(2) =10a(3) =23a(4) =76a(5) =102a(6) =442a(7) =695a(8) =1792a(9) =2828a(10) =11254a(11) =13334a(12) =53236a(13) =65418a(14) =155110a(15) =347319a(16) =1114096a(17) =1259328a(18) =4980718a(19) =6223148a(20) =15033700a(21) =27548678a(22) =96468970a(23) =108761942a(24) =352992576a(25) =529504212a(26) =1381165192a(27) =2314603370a(28) =7784628196