Sums of three consecutive pentagonal numbers.

Terms

a(0) =6a(1) =18a(2) =39a(3) =69a(4) =108a(5) =156a(6) =213a(7) =279a(8) =354a(9) =438a(10) =531a(11) =633a(12) =744a(13) =864a(14) =993a(15) =1131a(16) =1278a(17) =1434a(18) =1599a(19) =1773a(20) =1956a(21) =2148a(22) =2349a(23) =2559a(24) =2778a(25) =3006a(26) =3243a(27) =3489a(28) =3744a(29) =4008