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

A333030

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

Terms

    a(0) =3a(1) =21a(2) =132a(3) =432a(4) =951a(5) =1800a(6) =3069a(7) =4956a(8) =7569a(9) =11040a(10) =15585a(11) =21492a(12) =28971a(13) =38328a(14) =49527a(15) =62922a(16) =79113a(17) =98358a(18) =120939a(19) =147486a(20) =177873a(21) =212358a(22) =251823a(23) =296898a(24) =347709a(25) =404772a(26) =468189a(27) =538680a(28) =617439a(29) =704742

External references