Oblong numbers n such that n - 1 and n + 1 are both semiprime.

Terms

a(0) =56a(1) =552a(2) =870a(3) =1056a(4) =1190a(5) =1640a(6) =1892a(7) =2652a(8) =4032a(9) =5256a(10) =5402a(11) =6806a(12) =8372a(13) =9120a(14) =9506a(15) =9702a(16) =10920a(17) =11772a(18) =12656a(19) =12882a(20) =15006a(21) =15252a(22) =15500a(23) =16256a(24) =16770a(25) =17556a(26) =18632a(27) =23256a(28) =24492a(29) =27722