Cluster series for diamond.

Terms

a(0) =1a(1) =4a(2) =12a(3) =36a(4) =108a(5) =264a(6) =708a(7) =1668a(8) =4536a(9) =10926a(10) =28416a(11) =67824a(12) =172464a(13) =408484a(14) =1035932