1,2

Also structured pentakis dodecahedral numbers (vertex structure 7) (Cf. A100173 = alternate vertex).

a(n)=(1/6)*(54*n^3-72*n^2+24*n)

Contribution from Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Sep 08 2009: (Start)

a(n)=(3*(n-1)+1)^2*(3*(n-1)+3)/3

G.f.:x*(1+28*x+25*x^2)/(1-x)^4 (End)

Cf. A100164 = alternate vertex; A100145 for more on structured numbers.

Sequence in context: A100164 A048191 A097199 this_sequence A100173 A100172 A124998

Adjacent sequences: A100162 A100163 A100164 this_sequence A100166 A100167 A100168

easy,nonn

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