Semiprimes of the form (2*p+1)*(p-1)/2, p prime.

Terms

a(0) =22a(1) =115a(2) =517a(3) =6847a(4) =31951a(5) =128701a(6) =516601a(7) =1037851a(8) =2070001a(9) =4156501a(10) =4254937a(11) =6045451a(12) =7945351a(13) =8425957a(14) =8777887a(15) =9137017a(16) =13124317a(17) =14278951a(18) =14460907a(19) =14920837a(20) =24194101a(21) =29146501a(22) =31795501a(23) =47592751a(24) =48758797a(25) =50108701