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%I #26 May 20 2020 12:42:36
%S 1,2,3,6,9,18,27,58,99,316,936,20225,410571,50745729,2993355213,
%T 1701561156737,444491521018441,650424404724148930,
%U 430363737398835017296,2886485242642120438501318,8838475960755164592843156768,152938120727373876718042362054465
%N Number of simple graphs on n vertices with each component regular.
%H N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>
%F This sequence is the Euler transformation of A005177.
%F a(n) = A005177(n) + A165648(n).
%e The a(1)=1 graph is: K_1.
%e The a(2)=2 graphs are: 2K_1, K_2.
%e The a(3)=3 graphs are: 3K_1, K_1+K_2, K_3.
%e The a(4)=6 graphs are: 4K_1, 2K_1+K_2, K_1+K_3, 2K_2, C_4, K_4.
%t A005177 = Cases[Import["https://oeis.org/A005177/b005177.txt", "Table"], {_, _}][[All, 2]];
%t etr[p_] := Module[{b}, b[n_] := b[n] = If[n == 0, 1, Sum[DivisorSum[j, # p[#]&] b[n - j], {j, 1, n}]/n]; b];
%t a = etr[A005177[[#+1]]&];
%t a /@ Range[16] (* _Jean-François Alcover_, Dec 02 2019 *)
%Y Row sums of A275420.
%K nonn,hard
%O 1,2
%A _Jason Kimberley_, Sep 23 2009
%E Terms a(17) and beyond from _Andrew Howroyd_, May 20 2020
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