1,2

a(n)=(1/6)*(21*n^3-27*n^2+12*n)

Cf. A100157 = alternate vertex; A100145 for more on structured numbers.

Sequence in context: A100174 A120371 A062022 this_sequence A063492 A051799 A140184

Adjacent sequences: A100168 A100169 A100170 this_sequence A100172 A100173 A100174

easy,nonn

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