A301739 The number of trees with 4 nodes labeled by positive integers, where each tree's label sum is n.
2, 4, 10, 17, 30, 44, 67, 91, 126, 163, 213, 265, 333, 403, 491, 582, 693, 807, 944, 1084, 1249, 1418, 1614, 1814, 2044, 2278, 2544, 2815, 3120, 3430, 3777, 4129, 4520, 4917, 5355, 5799, 6287, 6781, 7321, 7868, 8463, 9065, 9718, 10378, 11091, 11812, 12588, 13372, 14214, 15064
Offset: 4
Examples
a(4)=2 because there is a linear tree with all labels equal 1 and the star tree with all labels equal to 1.
Links
- Index entries for linear recurrences with constant coefficients, signature (1,2,-1,-2,-1,2,1,-1).
Crossrefs
4th column of A303841.
Programs
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Maple
x^4*(2+2*x+2*x^2+x^3+x^4)/(1+x)^2/(x-1)^4/(1+x+x^2) ; taylor(%,x=0,80) ; gfun[seriestolist](%) ;
Comments