A055341 Number of mobiles (circular rooted trees) with n nodes and 3 leaves.

1, 3, 8, 19, 37, 66, 110, 172, 257, 371, 518, 705, 939, 1226, 1574, 1992, 2487, 3069, 3748, 4533, 5435, 6466, 7636, 8958, 10445, 12109, 13964, 16025, 18305, 20820, 23586, 26618, 29933, 33549, 37482, 41751, 46375, 51372, 56762, 62566, 68803

Offset: 4

Author

Christian G. Bower, May 14 2000

Keywords

• nonn

Links

• Index entries for sequences related to mobiles
• Index entries for linear recurrences with constant coefficients, signature (3,-2,-1,0,1,2,-3,1).

Crossrefs

Column 3 of A055340.

Programs

Maple

A055341 := proc(n)
    n^2/12+n/2-215/288+n^4/48-n^3/9-(-1)^n/32-2*A049347(n)/9 ;
end proc:
seq(A055341(n),n=4..40 ) ; # reuses code of A049347 R. J. Mathar, Feb 14 2025

Formula

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