Numbers whose base-7 representation contains exactly three 1's.

Terms

a(0) =57a(1) =351a(2) =393a(3) =399a(4) =401a(5) =402a(6) =403a(7) =404a(8) =405a(9) =407a(10) =414a(11) =421a(12) =428a(13) =435a(14) =449a(15) =498a(16) =547a(17) =596a(18) =645a(19) =743a(20) =1086a(21) =1429a(22) =1772a(23) =2115a(24) =2409a(25) =2451a(26) =2457a(27) =2459a(28) =2460a(29) =2461