Slowest increasing sequence beginning with 1 whose digits satisfy the rule d*2.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =16a(5) =21a(6) =24a(7) =248a(8) =481a(9) =681a(10) =6212a(11) =16212a(12) =42421a(13) =242484a(14) =842484a(15) =8168168a(16) =48168162a(17) =121621216a(18) =816212162a(19) =1242421242a(20) =4212162124a(21) =24212424848a(22) =42484842421a(23) =242484842484a(24) =816816848168