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%I #9 Sep 04 2017 19:25:26
%S 0,0,0,3,0,30,360,6930,196728,8115660,433362960,28552545945,
%T 2276033387760,216132739612218,24118774853584320,3125242929676107240,
%U 465357404934002231280,78908446775174591638440
%N Number of labeled n-node 4-valent graphs containing 3 double edges, a distinguished unordered pair of which are adjacent.
%D R. C. Read and N. C. Wormald, Number of labeled 4-regular graphs, J. Graph Theory, 4 (1980), 203-212.
%F Read and Wormald give recurrence relations involving all sequences A005815 and A058830-A058837 (see the Maple program). - _Emeric Deutsch_, Jan 26 2005
%p a[0]:=1: b[0]:=0: c[0]:=0: d[0]:=0: e[0]:=0: f[0]:=0: g[0]:=0: h[0]:=0: i[0]:=0: for p from 1 to 20 do a[p]:=((p-1)*(2*p-9)*a[p-1]+(2*p-8)*b[p-1]+c[p-1])/3: b[p]:=(6*p*(p-1)*a[p-1]+4*p*b[p-1]+p*d[p-1])/2: c[p]:=(6*p*(p-3)*b[p-1]+8*p*c[p-1]+4*p*d[p-1]+p*e[p-1])/4: d[p]:=p*b[p-1]+p*f[p-1]:e[p]:=(4*p*c[p-1]+4*p*d[p-1]+2*p*g[p-1]+p*(p-1)*(p-2)*a[p-3])/2:f[p]:=p*(p-1)*((4*p-8)*a[p-2]+2*b[p-2]+h[p-2])/2: g[p]:=p*(p-1)*(4*(p-3)*b[p-2]+4*c[p-2]+4*d[p-2]+2*f[p-2]+i[p-2])/2:h[p]:=p*((2*p-2)*a[p-1]+b[p-1]): i[p]:=p*((2*p-4)*b[p-1]+2*c[p-1]+2*d[p-1]+f[p-1]+h[p-1]): od: seq(e[n],n=0..20); # A058833(n)=e[n] - _Emeric Deutsch_, Jan 26 2005
%Y Cf. A005815, A058830, A058831, A058832, A058834, A058835, A058836, A058837.
%K nonn,easy
%O 0,4
%A _N. J. A. Sloane_, Jan 05 2001
%E More terms from _Emeric Deutsch_, Jan 26 2005
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