Positive numbers which are one less than a perfect square that is also another power.

Terms

a(0) =15a(1) =63a(2) =80a(3) =255a(4) =624a(5) =728a(6) =1023a(7) =1295a(8) =2400a(9) =4095a(10) =6560a(11) =9999a(12) =14640a(13) =15624a(14) =16383a(15) =20735a(16) =28560a(17) =38415a(18) =46655a(19) =50624a(20) =59048a(21) =65535a(22) =83520a(23) =104975a(24) =117648a(25) =130320a(26) =159999a(27) =194480a(28) =234255a(29) =262143