Coordination sequence for diamond.

Terms

a(0) =1a(1) =4a(2) =12a(3) =24a(4) =42a(5) =64a(6) =92a(7) =124a(8) =162a(9) =204a(10) =252a(11) =304a(12) =362a(13) =424a(14) =492a(15) =564a(16) =642a(17) =724a(18) =812a(19) =904a(20) =1002a(21) =1104a(22) =1212a(23) =1324a(24) =1442a(25) =1564a(26) =1692a(27) =1824a(28) =1962a(29) =2104