1,1

a(n)=[(4*n^2-8*n-9)/3]

For n=5, a(5)=17; n=114, a(114)=17021

Cf. A154618

Sequence in context: A090796 A089629 A007349 this_sequence A069755 A076727 A146870

Adjacent sequences: A154613 A154614 A154615 this_sequence A154617 A154618 A154619

nonn

Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Jan 18 2009