Numbers k such that 5 and 6 occur juxtaposed in the base-9 representation of k but not of k+1.

Terms

a(0) =51a(1) =59a(2) =132a(3) =140a(4) =213a(5) =221a(6) =294a(7) =302a(8) =375a(9) =383a(10) =456a(11) =467a(12) =539a(13) =545a(14) =618a(15) =626a(16) =699a(17) =707a(18) =780a(19) =788a(20) =861a(21) =869a(22) =942a(23) =950a(24) =1023a(25) =1031a(26) =1104a(27) =1112a(28) =1185a(29) =1196