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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
OFFSET
0,4
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
Sequence in context: A130878 A104422 A026547 * A058567 A115376 A076650
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Mar 17 2003
STATUS
approved