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Vincenzo Librandi, Table of n, a(n) for n = 1..10000
a(n) = (1/6)*(10*n^3-9*n^2+5*n).
G.f.: x*(1+5*x+4*x^2)/(1-x)^4. - Colin Barker, Jan 19 2012
(MAGMA) [(1/6)*(10*n^3-9*n^2+5*n): n in [1..40]]; // Vincenzo Librandi, Aug 18 2011
Cf. A004126 = alternate vertex; A000447 = structured diamonds; A100145 for more on structured numbers).
Sequence in context: A139275 A236370 A133547 * A106598 A014816 A147691
Adjacent sequences: A100176 A100177 A100178 * A100180 A100181 A100182
James A. Record (james.record(AT)gmail.com), Nov 07 2004