OFFSET
2,12
REFERENCES
F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 80, Problem 3.9.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 2..1226 (rows 2..50)
FORMULA
G.f.: A(x, y)=(1-x+x*y)*B(x, y)+(1/2)*(B(x^2, y^2)-B(x, y)^2), where B(x, y) is g.f. of A055277.
EXAMPLE
Triangle begins:
n=2: 1
n=3: 1 0
n=4: 1 1 0
n=5: 1 1 1 0
n=6: 1 2 2 1 0
n=7: 1 3 4 2 1 0
n=8: 1 4 8 6 3 1 0
n=9: 1 5 14 14 9 3 1 0
n=10: 1 7 23 32 26 12 4 1 0
n=11: 1 8 36 64 66 39 16 4 1 0
n=12: 1 10 54 123 158 119 60 20 5 1 0
n=13: 1 12 78 219 350 325 202 83 25 5 1 0
PROG
(PARI)
EulerMT(u)={my(n=#u, p=x*Ser(u), vars=variables(p)); Vec(exp( sum(i=1, n, substvec(p + O(x*x^(n\i)), vars, apply(v->v^i, vars))/i ))-1)}
T(n)={my(u=[y]); for(n=2, n, u=concat([y], EulerMT(u))); my(r=x*Ser(u), v=Vec(r*(1-x+x*y) + (substvec(r, [x, y], [x^2, y^2]) - r^2)/2)); vector(n-1, k, Vecrev(v[1+k]/y^2, k))}
{ my(A=T(10)); for(n=1, #A, print(A[n])) }
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Christian G. Bower, May 09 2000
STATUS
approved