

A185395


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


4



0, 0, 0, 1, 3, 3, 4, 9, 9, 9, 18, 18, 16, 30, 30, 25, 45, 45, 36, 63, 63, 49, 84, 84, 64, 108, 108, 81, 135, 135, 100, 165, 165, 121, 198, 198, 144, 234, 234, 169, 273, 273, 196, 315, 315, 225, 360, 360, 256
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OFFSET

0,5


COMMENTS

Expansion of ((x+x^2)/(1x^3))^k with k = 3 ; for k = 1 see A011655, for k = 2 see A186731, for k = 4 see A185292.
Column k = 3 of triangle in A198295.


LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,0,3,0,0,3,0,0,1).


FORMULA

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


MATHEMATICA

LinearRecurrence[{0, 0, 3, 0, 0, 3, 0, 0, 1}, {0, 0, 0, 1, 3, 3, 4, 9, 9}, 50] (* Harvey P. Dale, Jan 23 2013 *)


PROG

(PARI) x='x+O('x^50); concat([0, 0, 0], Vec((x*(1+x)/(1x^3))^3)) \\ G. C. Greubel, Jun 29 2017


CROSSREFS

Cf. A000217, A000290, A011655, A045943, A186731, A185292, A198295.
Sequence in context: A183501 A086239 A016605 * A060372 A128036 A045794
Adjacent sequences: A185392 A185393 A185394 * A185396 A185397 A185398


KEYWORD

easy,nonn


AUTHOR

Philippe Deléham, Jan 21 2012


STATUS

approved



