19
Small World Networks:
 & 6 degrees of separation
vEdelman, Eriksson, Strang
vEigenvalues of A=T+PTP’,  P=randperm(n)
v                                       Incidence matrix of graph with two
v         superimposed  cycles.   
v
v                              
vWigner style derivation counts number of paths on a tree starting and ending at the same point (tree = no accidents!)  (McKay)
vWe first discovered the formula using the superseeker
vCatalan number answer d2n-1-S d2j-1(d-1)n-j+1Cn-j
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v