a(n) is the number of ways to select an ordered pair of subsets of {2,...,n} such that each pair of elements from different subsets are relatively prime.
A260185
a(n) is the number of ways to select an ordered pair of subsets of {2,...,n} such that each pair of elements from different subsets are relatively prime.
Terms
- a(0) =1a(1) =3a(2) =9a(3) =21a(4) =63a(5) =111a(6) =333a(7) =693a(8) =1521a(9) =2577a(10) =7731a(11) =13491a(12) =40473a(13) =67833a(14) =119241a(15) =239481a(16) =718443a(17) =1340523a(18) =4021569a(19) =7494849a(20) =13356657a(21) =22271409a(22) =66814227a(23) =130266387a(24) =268286823a(25) =447212583a(26) =896472063a(27) =1684872063a(28) =5054616189a(29) =9566769789
External references
- oeis: A260185