4th power analog of Keith numbers.

Terms

a(0) =1a(1) =7a(2) =19a(3) =20a(4) =22a(5) =25a(6) =28a(7) =36a(8) =77a(9) =107a(10) =110a(11) =175a(12) =789a(13) =1528a(14) =1932a(15) =3778a(16) =5200a(17) =7043a(18) =8077a(19) =38855a(20) =41234a(21) =44884a(22) =49468a(23) =204386a(24) =763283a(25) =9423515a(26) =73628992a(27) =87146144a(28) =146124072a(29) =146293356