|
|
A297713
|
|
Number of minimal edge covers in the n-dipyramidal graph.
|
|
3
|
|
|
1, 6, 24, 74, 180, 464, 1113, 2646, 6360, 15222, 36795, 89584, 219635, 542320, 1346881, 3361998, 8427172, 21195416, 53455740, 135112332, 342093443, 867325032, 2201286622, 5591469852, 14211796995, 36139507614, 91934054637, 233934039872, 595393224041, 1515602413390
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
Sequence extrapolated to n=1 using recurrence. - Andrew Howroyd, Jun 26 2018
|
|
LINKS
|
Eric Weisstein's World of Mathematics, Matching
Index entries for linear recurrences with constant coefficients, signature (4, 1, -12, -15, 24, 49, 6, -73, -76, 5, 80, 72, 14, -30, -34, -19, -6, -1).
|
|
FORMULA
|
G.f.: x*(1 + x)*(1 + x - 2*x^2 - 14*x^3 - 39*x^4 + 63*x^5 + 69*x^6 + 55*x^7 - 39*x^8 - 85*x^9 - 118*x^10 - 102*x^11 - 63*x^12 - 27*x^13 - 7*x^14 - x^15)/((1 - x^2 - x^3)^3*(1 - x - x^2 - x^3)^2*(1 - 2*x - x^2 - x^3)). - Andrew Howroyd, Jun 26 2018
a(n) = 4*a(n-1) + a(n-2) - 12*a(n-3) - 15*a(n-4) + 24*a(n-5) + 49*a(n-6) + 6*a(n-7) - 73*a(n-8) - 76*a(n-9) + 5*a(n-10) + 80*a(n-11) + 72*a(n-12) + 14*a(n-13) - 30*a(n-14) - 34*a(n-15) - 19*a(n-16) - 6*a(n-17) - a(n-18). - Eric W. Weisstein, Jun 27 2018
|
|
MATHEMATICA
|
LinearRecurrence[{4, 1, -12, -15, 24, 49, 6, -73, -76, 5, 80, 72, 14, -30, -34, -19, -6, -1}, {1, 6, 24, 74, 180, 464, 1113, 2646, 6360, 15222, 36795, 89584, 219635, 542320, 1346881, 3361998, 8427172, 21195416}, 30]
CoefficientList[Series[-(1 + x) (-1 - x + 2 x^2 + 14 x^3 + 39 x^4 - 63 x^5 - 69 x^6 - 55 x^7 + 39 x^8 + 85 x^9 + 118 x^10 + 102 x^11 + 63 x^12 + 27 x^13 + 7 x^14 + x^15)/((-1 + x^2 + x^3)^3 (-1 + x + x^2 + x^3)^2 (-1 + 2 x + x^2 + x^3)), {x, 0, 20}], x]
|
|
PROG
|
(PARI) Vec((1 + x)*(1 + x - 2*x^2 - 14*x^3 - 39*x^4 + 63*x^5 + 69*x^6 + 55*x^7 - 39*x^8 - 85*x^9 - 118*x^10 - 102*x^11 - 63*x^12 - 27*x^13 - 7*x^14 - x^15)/((1 - x^2 - x^3)^3*(1 - x - x^2 - x^3)^2*(1 - 2*x - x^2 - x^3)) + O(x^40)) \\ Andrew Howroyd, Jun 26 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|