0,4

4*A091055(n) counts walks of length n between non-adjacent vertices of the Johnson graph J(5,2). 6^n=A091054(n)+6*A091055(n)+3*4*A091056(n).

a(n)=6^n/40+(-2)^n/24-1/15

Sequence in context: A050830 A146263 A050915 this_sequence A015544 A083076 A128418

Adjacent sequences: A091053 A091054 A091055 this_sequence A091057 A091058 A091059

easy,nonn

Paul Barry (pbarry(AT)wit.ie), Dec 17 2003