Powers of sqrt(17) rounded down.

Terms

a(0) =1a(1) =4a(2) =17a(3) =70a(4) =289a(5) =1191a(6) =4913a(7) =20256a(8) =83521a(9) =344365a(10) =1419857a(11) =5854220a(12) =24137569a(13) =99521746a(14) =410338673a(15) =1691869691a(16) =6975757441a(17) =28761784747a(18) =118587876497a(19) =488950340714