a(n) = binomial(n, smallest non-divisor of n).

Terms

a(0) =0a(1) =0a(2) =3a(3) =4a(4) =10a(5) =15a(6) =21a(7) =56a(8) =36a(9) =120a(10) =55a(11) =792a(12) =78a(13) =364a(14) =105a(15) =560a(16) =136a(17) =3060a(18) =171a(19) =1140a(20) =210a(21) =1540a(22) =253a(23) =42504a(24) =300a(25) =2600a(26) =351a(27) =3276a(28) =406a(29) =27405