A011929 - OEIS

A011929

a(n) = floor(n(n-1)(n-2)(n-3)/19).

0, 0, 0, 0, 1, 6, 18, 44, 88, 159, 265, 416, 625, 903, 1264, 1724, 2298, 3006, 3865, 4896, 6120, 7560, 9240, 11185, 13422, 15978, 18884, 22168, 25863, 30001, 34616, 39745, 45423, 51688, 58580, 66138, 74406, 83425, 93240, 103896, 115440, 127920, 141385

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OFFSET

0,6

LINKS

Table of n, a(n) for n=0..42.

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

FORMULA

From Chai Wah Wu, Aug 02 2020: (Start)

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) + a(n-19) - 4*a(n-20) + 6*a(n-21) - 4*a(n-22) + a(n-23) for n > 22.

G.f.: x^4*(x^2 + 1)^2*(-x^14 - 2*x^13 + 2*x^12 - 3*x^9 - x^8 + 4*x^7 - x^6 - 3*x^5 + 2*x^2 - 2*x - 1)/(x^23 - 4*x^22 + 6*x^21 - 4*x^20 + x^19 - x^4 + 4*x^3 - 6*x^2 + 4*x - 1). (End)

MATHEMATICA

Table[Floor[n(n - 1)(n - 2)(n - 3)/19], {n, 0, 50}] (* Stefan Steinerberger, Apr 10 2006 *)

PROG

(PARI) a(n)=n*(n-1)*(n-2)*(n-3)\19 \\ Charles R Greathouse IV, Oct 18 2022

CROSSREFS

Sequence in context: A184630 A009957 A344992 * A070735 A136028 A083719

Adjacent sequences: A011926 A011927 A011928 * A011930 A011931 A011932

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Stefan Steinerberger, Apr 10 2006

STATUS

approved