Largest number k such that k^2 divides A007781(6n+1).

Terms

a(0) =19a(1) =61a(2) =127a(3) =217a(4) =331a(5) =469a(6) =631a(7) =817a(8) =1027a(9) =1261a(10) =1519a(11) =1801a(12) =2107a(13) =2437a(14) =2791a(15) =3169a(16) =3571a(17) =3997a(18) =4447a(19) =4921a(20) =5419a(21) =5941a(22) =6487a(23) =7057a(24) =7651a(25) =8269a(26) =8911a(27) =9577a(28) =10267a(29) =10981