Number of nonempty subsets of {1, 2, ..., n} with <= 4 pairwise coprime elements.

Terms

a(0) =1a(1) =3a(2) =7a(3) =11a(4) =23a(5) =27a(6) =53a(7) =68a(8) =97a(9) =109a(10) =193a(11) =208a(12) =345a(13) =382a(14) =437a(15) =506a(16) =785a(17) =827a(18) =1224a(19) =1310a(20) =1472a(21) =1590a(22) =2253a(23) =2346a(24) =2892a(25) =3100a(26) =3568a(27) =3784a(28) =5070a(29) =5163