Number of triangular regions in an equilateral triangular "frame" of size n (see Comments in A328526 for definition).

A333032

Number of triangular regions in an equilateral triangular "frame" of size n (see Comments in A328526 for definition).

Terms

    a(0) =1a(1) =12a(2) =48a(3) =147a(4) =291a(5) =519a(6) =879a(7) =1383a(8) =2079a(9) =3039a(10) =4359a(11) =5991a(12) =7983a(13) =10515a(14) =13731a(15) =17571a(16) =22131a(17) =27543a(18) =33951a(19) =41271a(20) =49599a(21) =59355a(22) =70779a(23) =83499a(24) =97611a(25) =113763a(26) =132243a(27) =152619a(28) =175035a(29) =199707

External references