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A291053 Number of maximal irredundant sets in the n-Andrasfai graph. 3
2, 10, 28, 88, 217, 493, 989, 1794, 3016, 4785, 7256, 10612, 15067, 20869, 28303, 37694, 49410, 63865, 81522, 102896, 128557, 159133, 195313, 237850, 287564, 345345, 412156, 489036, 577103, 677557, 791683, 920854, 1066534, 1230281, 1413750, 1618696, 1846977, 2100557 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..38.

Eric Weisstein's World of Mathematics, Andrasfai Graph

Eric Weisstein's World of Mathematics, Maximal Irredundant Set

FORMULA

From Eric W. Weisstein, Aug 21 2017: (Start)

a(n) = (-3120 + 10932*n - 4970*n^2 + 765*n^3 - 10*n^4 + 3*n^5)/120 for n > 3.

a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n > 9.

G.f.: (x (2 - 2 x - 2 x^2 + 30 x^3 - 61 x^4 + 89 x^5 - 112 x^6 + 77 x^7 - 18 x^8))/(-1 + x)^6.

(End)

MATHEMATICA

Table[Piecewise[{{2, n == 1}, {10, n == 2}, {28, n == 3}}, (-3120 + 10932 n - 4970 n^2 + 765 n^3 - 10 n^4 + 3 n^5)/120], {n, 20}]

Join[{2, 10, 28}, LinearRecurrence[{6, -15, 20, -15, 6, -1}, {88, 217, 493, 989, 1794, 3016}, 20]] (* Eric W. Weisstein, Aug 21 2017 *)

CoefficientList[Series[(2 - 2 x - 2 x^2 + 30 x^3 - 61 x^4 + 89 x^5 - 112 x^6 + 77 x^7 - 18 x^8)/(-1 + x)^6, {x, 0, 20}], x] (* Eric W. Weisstein, Aug 21 2017 *)

CROSSREFS

Cf. A285272, A290587, A291053.

Sequence in context: A252591 A296849 A296380 * A104657 A000900 A124023

Adjacent sequences:  A291050 A291051 A291052 * A291054 A291055 A291056

KEYWORD

nonn,

AUTHOR

Eric W. Weisstein, Aug 17 2017

EXTENSIONS

a(9)-a(20) from Andrew Howroyd, Aug 19 2017

a(21) and above from Eric W. Weisstein, Aug 21 2017

STATUS

approved

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Last modified February 18 00:19 EST 2019. Contains 320237 sequences. (Running on oeis4.)