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%I #28 Mar 18 2020 09:00:45
%S 1,0,0,0,0,0,0,0,1,0,2,2,12,31,220,1606,16829,193900,2452820,32670332,
%T 456028489,6636066134,100135577994,1582718914660
%N Number of not necessarily connected 4-regular simple graphs on n vertices with girth at least 4.
%H Jason Kimberley, <a href="/wiki/User:Jason_Kimberley/E_girth_ge_4">Not necessarily connected k-regular graphs with girth at least 4</a>
%H Jason Kimberley, <a href="/wiki/User:Jason_Kimberley/E_k-reg_girth_ge_g_index">Index of sequences counting not necessarily connected k-regular simple graphs with girth at least g</a>
%F This sequence is the Euler transformation of A033886.
%F a(n) = A033886(n) + A185244(n).
%t A033886 = Cases[Import["https://oeis.org/A033886/b033886.txt", "Table"], {_, _}][[All, 2]];
%t (* EulerTransform is defined in A005195 *)
%t EulerTransform[Rest @ A033886] (* _Jean-François Alcover_, Dec 04 2019, updated Mar 18 2020 *)
%Y 4-regular simple graphs with girth at least 4: A033886 (connected), A185244 (disconnected), this sequence (not necessarily connected).
%Y Not necessarily connected k-regular simple graphs with girth at least 4: A185314 (any k), A185304 (triangle); specified degree k: A008484 (k=2), A185334 (k=3), this sequence (k=4), A185354 (k=5), A185364 (k=6).
%K nonn,hard,more
%O 0,11
%A _Jason Kimberley_, Nov 03 2011
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