1,2

a(n)=(1/6)*(20*n^3-24*n^2+10*n)

Cf. A005915 = alternate vertex; A100145 for more on structured numbers.

Sequence in context: A084195 A033856 A143861 this_sequence A120371 A062022 A158058

Adjacent sequences: A100171 A100172 A100173 this_sequence A100175 A100176 A100177

easy,nonn

James A. Record (james.record(AT)gmail.com). Nov 07, 2004.

Formula corrected by Helena Verrill (verrill(AT)math.lsu.edu), Mar 23 2007