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A053126 Binomial coefficients binomial(2*n-3,4). 9
5, 35, 126, 330, 715, 1365, 2380, 3876, 5985, 8855, 12650, 17550, 23751, 31465, 40920, 52360, 66045, 82251, 101270, 123410, 148995, 178365, 211876, 249900, 292825, 341055, 395010, 455126, 521855, 595665, 677040, 766480 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,1

COMMENTS

a(n)= A053123(n,4), n >= 4; a(n) := 0, n=0..3. (fifth column of shifted Chebyshev's S-triangle, decreasing order)

Number of intersections of diagonals in the interior of regular (2n-3)-gon. - Philippe Deléham, Jun 07 2013

REFERENCES

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings).

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 4..200

Milan Janjic, Two Enumerative Functions

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].

Index entries for sequences related to Chebyshev polynomials.

FORMULA

a(n) = binomial(2*n-3, 4) if n >= 4 else 0; G.f.: (5+10*x+x^2)/(1-x)^5.

a(n) = A006561(2n-3). - Philippe Deléham, Jun 07 2013

PROG

(MAGMA) [Binomial(2*n-3, 4): n in [4..40]]; // Vincenzo Librandi, Oct 07 2011

CROSSREFS

Cf. A053123, A002492.

Sequence in context: A161199 A111877 A179337 * A096743 A026697 A000910

Adjacent sequences:  A053123 A053124 A053125 * A053127 A053128 A053129

KEYWORD

nonn,easy

AUTHOR

Wolfdieter Lang

STATUS

approved

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Last modified August 18 22:17 EDT 2018. Contains 313840 sequences. (Running on oeis4.)