Composite numbers of the form k^2+k+1 all of whose prime factors are of that same form.

Terms

a(0) =21a(1) =91a(2) =273a(3) =343a(4) =507a(5) =651a(6) =1333a(7) =4557a(8) =6321a(9) =6643a(10) =27391a(11) =36673a(12) =50851a(13) =65793a(14) =83811a(15) =105301a(16) =139503a(17) =190533a(18) =194923a(19) =217623a(20) =234741a(21) =391251a(22) =545383a(23) =1647373a(24) =1961401a(25) =2032051a(26) =2376223a(27) =4517751a(28) =6118203a(29) =6484663