A241929 Number of inequivalent colorings of the Fano plane with n colors.

1, 10, 60, 264, 930, 2766, 7205, 16880, 36279, 72610, 136906, 245400, 421200, 696294, 1113915, 1731296, 2622845, 3883770, 5634184, 8023720, 11236686, 15497790, 21078465, 28303824, 37560275, 49303826, 64069110, 82479160, 105255964, 133231830, 167361591, 208735680

Offset

1,2

Links

Table of n, a(n) for n=1..32.

Wikipedia, Fano plane

Index entries for linear recurrences with constant coefficients, signature (8,-28,56,-70,56,-28,8,-1).

Formula

a(n) = n*(n^2+6)*(n^4+15*n^2+8)/168.

G.f.: x*(x^2+x+1)*(x^4+x^3+6*x^2+x+1) / (x-1)^8. - Colin Barker, May 03 2014

Prog

(PARI) Vec(x*(x^2+x+1)*(x^4+x^3+6*x^2+x+1)/(x-1)^8 + O(x^100)) \\ Colin Barker, May 03 2014

Crossrefs

Sequence in context: A283727 A349415 A228581 * A278721 A341366 A004406

Adjacent sequences: A241926 A241927 A241928 * A241930 A241931 A241932

Keyword

nonn,easy

Author

Philippe Deléham, May 02 2014

Status

approved