s(k)=1, where s=A030787.

Terms

a(0) =2a(1) =4a(2) =6a(3) =12a(4) =23a(5) =24a(6) =31a(7) =40a(8) =41a(9) =51a(10) =63a(11) =65a(12) =78a(13) =80a(14) =95a(15) =114a(16) =134a(17) =137a(18) =156a(19) =159a(20) =164a(21) =182a(22) =185a(23) =188a(24) =211a(25) =214a(26) =242a(27) =245a(28) =275a(29) =278