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A306351 Number of ways to split an n-cycle into connected subgraphs all having at least 4 vertices. 8
1, 0, 0, 0, 1, 1, 1, 1, 5, 10, 16, 23, 35, 53, 78, 111, 157, 222, 313, 438, 610, 848, 1178, 1634, 2263, 3131, 4330, 5986, 8272, 11427, 15782, 21794, 30093, 41548, 57359, 79183, 109307, 150887, 208279, 287496, 396838, 547761, 756077, 1043611, 1440488, 1988289 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,9

LINKS

Table of n, a(n) for n=0..45.

Index entries for linear recurrences with constant coefficients, signature (3,-3,1,1,-2,1).

FORMULA

G.f.: (2*x^9-3*x^8+x^3-3*x^2+3*x-1)/((x^4+x-1)*(x-1)^2). - Alois P. Heinz, Feb 10 2019

EXAMPLE

The a(7) = 1 through a(9) = 10 partitions:

  {{1234567}}  {{12345678}}    {{123456789}}

               {{1234}{5678}}  {{1234}{56789}}

               {{1238}{4567}}  {{12345}{6789}}

               {{1278}{3456}}  {{12349}{5678}}

               {{1678}{2345}}  {{12389}{4567}}

                               {{1239}{45678}}

                               {{12789}{3456}}

                               {{1289}{34567}}

                               {{16789}{2345}}

                               {{1789}{23456}}

MATHEMATICA

cycedsprop[n_, k_]:=Union[Sort/@Join@@Table[1+Mod[Range[i, j]-1, n], {i, n}, {j, i+k, n+i-1}]];

spsu[_, {}]:={{}}; spsu[foo_, set:{i_, ___}]:=Join@@Function[s, Prepend[#, s]&/@spsu[Select[foo, Complement[#, Complement[set, s]]=={}&], Complement[set, s]]]/@Cases[foo, {i, ___}];

Table[Length[spsu[cycedsprop[n, 3], Range[n]]], {n, 15}]

CROSSREFS

Column k = 3 of A323954.

Cf. A000325, A005251, A066982, A078012, A323950, A323951, A323953.

Sequence in context: A313940 A212455 A052905 * A215341 A194275 A026059

Adjacent sequences:  A306348 A306349 A306350 * A306352 A306353 A306354

KEYWORD

nonn,easy

AUTHOR

Gus Wiseman, Feb 10 2019

EXTENSIONS

More terms from Alois P. Heinz, Feb 10 2019

STATUS

approved

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Last modified December 10 20:48 EST 2019. Contains 329909 sequences. (Running on oeis4.)