Pinwheel numbers: a(n) = 2*n^2 + 6*n + 1.

Terms

a(0) =1a(1) =9a(2) =21a(3) =37a(4) =57a(5) =81a(6) =109a(7) =141a(8) =177a(9) =217a(10) =261a(11) =309a(12) =361a(13) =417a(14) =477a(15) =541a(16) =609a(17) =681a(18) =757a(19) =837a(20) =921a(21) =1009a(22) =1101a(23) =1197a(24) =1297a(25) =1401a(26) =1509a(27) =1621a(28) =1737a(29) =1857