Numbers whose base-7 representation has the same nonzero number of 1's and 3's.

Terms

a(0) =10a(1) =22a(2) =52a(3) =66a(4) =70a(5) =72a(6) =74a(7) =75a(8) =76a(9) =80a(10) =87a(11) =94a(12) =108a(13) =120a(14) =148a(15) =154a(16) =156a(17) =158a(18) =159a(19) =160a(20) =162a(21) =176a(22) =183a(23) =190a(24) =206a(25) =218a(26) =255a(27) =267a(28) =304a(29) =316