Toothpick sequence in the three-dimensional grid.

Terms

a(0) =0a(1) =1a(2) =3a(3) =7a(4) =15a(5) =23a(6) =31a(7) =39a(8) =55a(9) =87a(10) =143a(11) =175a(12) =191a(13) =199a(14) =215a(15) =247a(16) =303a(17) =359a(18) =423a(19) =503a(20) =655a(21) =887a(22) =1239a(23) =1383a(24) =1431a(25) =1463a(26) =1487a(27) =1527a(28) =1583a(29) =1639