Integers k such that A231589(k) = floor(k*(k-1)/4) - k.

Terms

a(0) =8a(1) =25a(2) =77a(3) =125a(4) =133a(5) =209a(6) =301a(7) =325a(8) =425a(9) =469a(10) =473a(11) =725a(12) =737a(13) =817a(14) =925a(15) =1025a(16) =1141a(17) =1273a(18) =1325a(19) =1525a(20) =1625a(21) =1793a(22) =1825a(23) =2125a(24) =2225a(25) =2425a(26) =2525a(27) =2725a(28) =2825a(29) =2881