a(0) = 1, a(n) = result of eliminating the digit 7 from the sum of all previous terms for n>=1.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =16a(6) =32a(7) =64a(8) =128a(9) =256a(10) =512a(11) =1024a(12) =2048a(13) =4096a(14) =8192a(15) =16384a(16) =3268a(17) =36036a(18) =202a(19) =224a(20) =2498a(21) =4996a(22) =9992a(23) =89984a(24) =19968a(25) =199936a(26) =39982a(27) =439854a(28) =8908a(29) =888616