|
Search: id:A060095
|
|
|
| A060095 |
|
Number of 7-block ordered bicoverings of an unlabeled n-set. |
|
+0
16
|
|
| 0, 0, 0, 0, 0, 1680, 27342, 208302, 1099602, 4636072, 16734438, 53810484, 158053119, 431305959, 1106791524, 2694914978, 6269281305, 14010246285, 30208869495, 63074014815, 127909521180, 252581107180, 486738385140
(list; graph; listen)
|
|
|
OFFSET
|
0,6
|
|
|
FORMULA
|
a(n) = binomial(n + 20, n) - 7*binomial(n + 14, 14) - 21*binomial(n + 10, 10) + 42*binomial(n + 9, 9) + 105*binomial(n + 6, 6) - 140*binomial(n + 5, 5) + 105*binomial(n + 4, 4) - 420*binomial(n + 3, 3) + 35*binomial(n + 2, 2) + 1050*binomial(n + 1, 1) - 1050*binomial(n, 0) + 300*binomial(n - 1, - 1); G.f.: y^5*( - 1680 - 7005635*y^7 + 5039622*y^6 - 2707236*y^5 + 1022210*y^4 - 232680*y^3 + 13080*y^2 + 7938*y - 5250*y^15 + 300*y^16 + 43050*y^14 - 6227505*y^9 + 4042780*y^10 + 7485450*y^8 - 219485*y^13 + 778260*y^12 - 2033220*y^11)/( - 1 + y)^21; E.g.f. for k-block ordered bicoverings of an unlabeled n-set is exp( - x - x^2/2*y/(1 - y))*Sum_{k = 0..inf} 1/(1 - y)^binomial(k, 2)*x^k/k!.
|
|
CROSSREFS
|
Cf. A060090-A060094, A060069, A060070, A060051-A060053, A002718, A059443, A003462, A059945-A059951.
Sequence in context: A098974 A109564 A093787 this_sequence A069331 A031629 A031760
Adjacent sequences: A060092 A060093 A060094 this_sequence A060096 A060097 A060098
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Vladeta Jovovic (vladeta(AT)Eunet.yu), Feb 26 2001
|
|
|
Search completed in 0.002 seconds
|
