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A081283 An interleaved sequence of pyramidal and polygonal numbers. 3
0, 1, 1, 5, 6, 16, 20, 40, 50, 85, 105, 161, 196, 280, 336, 456, 540, 705, 825, 1045, 1210, 1496, 1716, 2080, 2366, 2821, 3185, 3745, 4200, 4880, 5440, 6256, 6936, 7905, 8721, 9861, 10830, 12160, 13300, 14840, 16170, 17941, 19481, 21505, 23276, 25576, 27600 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (2,2,-6,0,6,-2,-2,1).

FORMULA

G.f.: x*(1+x^3)/((1-x)*(1-x^2)^4).

a(2*n) = A002415(n);  a(2*n+1) = A006007(n+1).

a(n) = (2*n+1-(-1)^n)*(2*n+5-(-1)^n)*(2*n^2+2*(5+(-1)^n)*n+27-11*(-1)^n)/1536. - Luce ETIENNE, Mar 11 2015

MAPLE

A081283:=n->(2*n+1-(-1)^n)*(2*n+5-(-1)^n)*(2*n^2+2*(5+(-1)^n)*n+27-11*(-1)^n)/1536: seq(A081283(n), n=0..80); # Wesley Ivan Hurt, Apr 18 2017

MATHEMATICA

CoefficientList[Series[x (1 + x^3) / ((1 - x) (1 - x^2)^4), {x, 0, 50}], x] (* Vincenzo Librandi, Aug 07 2013 *)

CROSSREFS

Cf. A081282, A081284.

Sequence in context: A130878 A104422 A026547 * A058567 A115376 A076650

Adjacent sequences:  A081280 A081281 A081282 * A081284 A081285 A081286

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Mar 17 2003

STATUS

approved

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Last modified March 26 00:27 EDT 2019. Contains 321479 sequences. (Running on oeis4.)