Number of subsets of {1,2,...,n-9} without differences equal to 3, 6 or 9.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =1a(9) =1a(10) =2a(11) =4a(12) =8a(13) =12a(14) =18a(15) =27a(16) =36a(17) =48a(18) =64a(19) =80a(20) =100a(21) =125a(22) =175a(23) =245a(24) =343a(25) =490a(26) =700a(27) =1000a(28) =1400a(29) =1960