a(n) is the smallest semiprime such that difference between a(n) and next semiprime, b(n), is n.

Terms

a(0) =9a(1) =4a(2) =6a(3) =10a(4) =69a(5) =15a(6) =26a(7) =169a(8) =146a(9) =237a(10) =95a(11) =1082a(12) =818a(13) =597a(14) =1603a(15) =2705a(16) =2078a(17) =4511a(18) =1418a(19) =2681a(20) =14545a(21) =13863a(22) =37551a(23) =6559a(24) =16053a(25) =55805a(26) =26707a(27) =17965a(28) =308918a(29) =32777