Number of subsets of {1,2,...,n} with relatively prime elements.

Terms

a(0) =1a(1) =2a(2) =5a(3) =11a(4) =26a(5) =53a(6) =116a(7) =236a(8) =488a(9) =983a(10) =2006a(11) =4016a(12) =8111a(13) =16238a(14) =32603a(15) =65243a(16) =130778a(17) =261566a(18) =523709a(19) =1047479a(20) =2095988a(21) =4192115a(22) =8386418a(23) =16772858a(24) =33550058a(25) =67100393a(26) =134209001a(27) =268418531a(28) =536853986a(29) =1073707991