Coordination sequence for C_3 lattice: a(n) = 16*n^2 + 2 (n>0), a(0)=1.

Terms

a(0) =1a(1) =18a(2) =66a(3) =146a(4) =258a(5) =402a(6) =578a(7) =786a(8) =1026a(9) =1298a(10) =1602a(11) =1938a(12) =2306a(13) =2706a(14) =3138a(15) =3602a(16) =4098a(17) =4626a(18) =5186a(19) =5778a(20) =6402a(21) =7058a(22) =7746a(23) =8466a(24) =9218a(25) =10002a(26) =10818a(27) =11666a(28) =12546a(29) =13458