Multiples of 3 that are one less than a perfect square.

Terms

a(0) =0a(1) =3a(2) =15a(3) =24a(4) =48a(5) =63a(6) =99a(7) =120a(8) =168a(9) =195a(10) =255a(11) =288a(12) =360a(13) =399a(14) =483a(15) =528a(16) =624a(17) =675a(18) =783a(19) =840a(20) =960a(21) =1023a(22) =1155a(23) =1224a(24) =1368a(25) =1443a(26) =1599a(27) =1680a(28) =1848a(29) =1935