|
|
A216367
|
|
G.f.: Sum_{n>=0} x^n / Product_{k=0..n} (1 - k*x)^2.
|
|
2
|
|
|
1, 1, 3, 10, 40, 184, 948, 5384, 33300, 222192, 1587512, 12071776, 97206544, 825343600, 7362067888, 68772244640, 670917511424, 6818719677952, 72038876668544, 789610228149632, 8963457852609984, 105211331721594368, 1275095788516589952, 15934546466314258688
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
COMMENTS
|
Compare to o.g.f. of Bell numbers: Sum_{n>=0} x^n / Product_{k=0..n} (1 - k*x).
|
|
LINKS
|
|
|
EXAMPLE
|
G.f.: A(x) = 1 + x + 3*x^2 + 10*x^3 + 40*x^4 + 184*x^5 + 948*x^6 +...
where
A(x) = 1 + x/(1-x)^2 + x^2/((1-x)*(1-2*x))^2 + x^3/((1-x)*(1-2*x)*(1-3*x))^2 + x^4/((1-x)*(1-2*x)*(1-3*x)*(1-4*x))^2 +...
|
|
MATHEMATICA
|
With[{nn=30}, CoefficientList[Series[Sum[x^n/Product[(1-k*x)^2, {k, 0, n}], {n, 0, nn}], {x, 0, nn}], x]] (* Harvey P. Dale, Dec 15 2018 *)
|
|
PROG
|
(PARI) {a(n)=polcoeff(sum(m=0, n, x^m/prod(k=1, m, 1-k*x +x*O(x^n))^2), n)}
for(n=0, 30, print1(a(n), ", "))
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|