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

A333031

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

Terms

    a(0) =3a(1) =10a(2) =58a(3) =183a(4) =408a(5) =777a(6) =1323a(7) =2142a(8) =3276a(9) =4773a(10) =6717a(11) =9264a(12) =12507a(13) =16554a(14) =21351a(15) =27090a(16) =34047a(17) =42318a(18) =52008a(19) =63453a(20) =76566a(21) =91371a(22) =108249a(23) =127608a(24) =149487a(25) =173982a(26) =201072a(27) =231225a(28) =265002a(29) =302487

External references