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A297665 Number of chordless cycles in the n-web graph. 0
3, 10, 17, 26, 37, 54, 81, 124, 191, 296, 463, 732, 1167, 1870, 3005, 4838, 7801, 12594, 20349, 32896, 53195, 86036, 139171, 225144, 364251, 589330, 953513, 1542770, 2496205, 4038894, 6535017, 10573828, 17108759, 27682496, 44791159, 72473556, 117264615, 189738070 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

LINKS

Table of n, a(n) for n=3..40.

Eric Weisstein's World of Mathematics, Chordless Cycle

Eric Weisstein's World of Mathematics, Web Graph

Index entries for linear recurrences with constant coefficients, signature (4, -6, 4, 0, -2, 1).

FORMULA

a(n) = 3*fibonacci(n-1)+n-1)-chebyshevu(n-2, 1/2)-5.

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - 2*a(n-5) + a(n-6).

G.f.: x*(-3 + 2*x + 5*x^2 - 6*x^3 + 5*x^4)/((-1 + x)^2*(-1 + 2*x - x^2 + x^4)).

MATHEMATICA

Table[3 (Fibonacci[n - 1] + n - 1) - ChebyshevU[n - 2, 1/2] - 5, {n, 3, 40}]

LinearRecurrence[{4, -6, 4, 0, -2, 1}, {3, 10, 17, 26, 37, 54}, 20]

CROSSREFS

Sequence in context: A047702 A219726 A017017 * A309347 A273235 A309351

Adjacent sequences:  A297662 A297663 A297664 * A297666 A297667 A297668

KEYWORD

nonn,easy

AUTHOR

Eric W. Weisstein, Jan 02 2018

STATUS

approved

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Last modified November 21 04:33 EST 2019. Contains 329350 sequences. (Running on oeis4.)