Number of obtuse triangles, distinct up to congruence, on a centered hexagonal grid of size n.

Terms

a(0) =0a(1) =1a(2) =15a(3) =72a(4) =220a(5) =528a(6) =1076a(7) =1965a(8) =3314a(9) =5254a(10) =7954a(11) =11589a(12) =16306a(13) =22349a(14) =29939a(15) =39305a(16) =50738a(17) =64462a(18) =80775a(19) =100096a(20) =122602a(21) =148748a(22) =178834a(23) =213268a(24) =252439a(25) =296857a(26) =346878a(27) =402778a(28) =465346a(29) =534966