|
| |
|
|
A095308
|
|
Number of walks of length n between two nodes at distance 3 in the cycle graph C_7.
|
|
1
| |
|
|
1, 1, 5, 6, 21, 28, 84, 121, 331, 507, 1300, 2093, 5110, 8568, 20129, 34885, 79477, 141494, 314489, 572264, 1246784, 2309385, 4950751, 9303411, 19684692, 37427313, 78354346, 150402700, 312168761, 603861897, 1244620149
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 3,3
|
|
|
COMMENTS
| In general 2^n/m*Sum(r,0,m-1,Cos(2Pi*k*r/m)Cos(2Pi*r/m)^n) is the number of walks of length n between two nodes at distance k in the cycle graph C_m. Here we have m=7 and k=3.
|
|
|
FORMULA
| a(n)= 2^n/7*Sum(r, 0, 6, Cos(6Pi*r/7)Cos(2Pi*r/7)^n) G.f.: x^3/((-1+2x)(-1-x+2x^2+x^3)) a(n)=a(n-1)+4a(n-2)-3a(n-3)-2a(n-4)
|
|
|
CROSSREFS
| Sequence in context: A057520 A060423 A037951 * A132796 A006492 A110344
Adjacent sequences: A095305 A095306 A095307 * A095309 A095310 A095311
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Herbert Kociemba (kociemba(AT)t-online.de), Jul 03 2004
|
| |
|
|
