Numbers n with property that 4 n^2 are squares arising in A158470.

Terms

a(0) =3a(1) =12a(2) =18a(3) =102a(4) =192a(5) =762a(6) =843a(7) =1332a(8) =1368a(9) =1587a(10) =2013a(11) =2307a(12) =2907a(13) =3702a(14) =3762a(15) =3798a(16) =3867a(17) =5367a(18) =5433a(19) =5622a(20) =5793a(21) =6117a(22) =7008a(23) =7758a(24) =8352a(25) =10488a(26) =11022a(27) =11523a(28) =12078a(29) =12303