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

A333033

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

Terms

    a(0) =0a(1) =0a(2) =24a(3) =102a(4) =252a(5) =504a(6) =867a(7) =1431a(8) =2214a(9) =3228a(10) =4509a(11) =6237a(12) =8481a(13) =11259a(14) =14445a(15) =18261a(16) =22935a(17) =28497a(18) =34980a(19) =42762a(20) =51708a(21) =61632a(22) =72795a(23) =85791a(24) =100611a(25) =117027a(26) =134874a(27) =154836a(28) =177402a(29) =202548

External references