Composites of form n^2 + n + 1.

Terms

a(0) =21a(1) =57a(2) =91a(3) =111a(4) =133a(5) =183a(6) =273a(7) =343a(8) =381a(9) =507a(10) =553a(11) =651a(12) =703a(13) =813a(14) =871a(15) =931a(16) =993a(17) =1057a(18) =1191a(19) =1261a(20) =1333a(21) =1407a(22) =1561a(23) =1641a(24) =1807a(25) =1893a(26) =1981a(27) =2071a(28) =2163a(29) =2257