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A210714 Number of disconnected regular simple graphs on n vertices with girth exactly 4. 1

%I #11 Jan 27 2020 07:36:52

%S 0,0,0,0,0,0,0,0,1,1,1,1,3,2,5,3,15,5,44,10,203,47,1415,1710,27771,

%T 197951,2613710,33117920,463707092,6709514282,102306345333,

%U 1597440872721

%N Number of disconnected regular simple graphs on n vertices with girth exactly 4.

%H Jason Kimberley, <a href="/wiki/User:Jason_Kimberley/D_k-reg_girth_eq_g_index">Index of sequences counting disconnected k-regular simple graphs with girth exactly g</a>

%F a(n) = A185214(n) - A185215(n).

%t A[s_Integer] := With[{s6 = StringPadLeft[ToString[s], 6, "0"]}, Cases[ Import["https://oeis.org/A" <> s6 <> "/b" <> s6 <> ".txt", "Table"], {_, _}][[All, 2]]];

%t A185214 = A@185214;

%t A185215 = A@185215;

%t a[n_] := A185214[[n + 1]] - A185215[[n + 1]];

%t a /@ Range[0, 31] (* _Jean-François Alcover_, Jan 27 2020 *)

%K nonn,more,hard

%O 0,13

%A _Jason Kimberley_, Dec 10 2012

%E a(31) corrected by the author, propagated from A185244, Jan 05 2013

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)