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A028294 a(n) = n^5 - (65/6)*n^4 + (173/6)*n^3 + (148/3)*n^2 - (862/3)*n + 265. 3
1, 20, 281, 1357, 4281, 10666, 22825, 43891, 77937, 130096, 206681, 315305, 465001, 666342, 931561, 1274671, 1711585, 2260236, 2940697, 3775301, 4788761, 6008290, 7463721, 9187627, 11215441, 13585576, 16339545, 19522081, 23181257, 27368606, 32139241 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,2

COMMENTS

Old name was: "Number of stacks of n pikelets, distance 5 flips from a well-ordered stack".

LINKS

Table of n, a(n) for n=4..34.

Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).

FORMULA

G.f.: x^4*(9*x^5-31*x^4-49*x^3+176*x^2+14*x+1) / (x-1)^6. - Colin Barker, Jun 04 2014

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). - Wesley Ivan Hurt, Aug 28 2015

E.g.f.: (x^5 -(5/6)*x^4 - (67/6)*x^3 + 75x^2 - 219 x + 265)*exp(x) + (3/2)*x^3 + (23/2)*x^2 - 46x - 265. - G. C. Greubel, Aug 29 2015

MAPLE

A028294:=n->n^5 - (65/6)*n^4 + (173/6)*n^3 + (148/3)*n^2 - (862/3)*n + 265: seq(A028294(n), n=4..40); # Wesley Ivan Hurt, Aug 28 2015

MATHEMATICA

CoefficientList[Series[(9*x^5 - 31*x^4 - 49*x^3 + 176*x^2 + 14*x + 1)/(x - 1)^6, {x, 0, 40}], x] (* Wesley Ivan Hurt, Aug 28 2015 *)

Table[n^5 - (65/6) n^4 + (173/6) n^3 + (148/3) n^2 - (862/3)n + 265, {n, 4, 40}] (* Vincenzo Librandi, Aug 29 2015 *)

PROG

(PARI) Vec(x^4*(9*x^5-31*x^4-49*x^3+176*x^2+14*x+1)/(x-1)^6 + O(x^100)) \\ Colin Barker, Jun 04 2014

(MAGMA) [n^5 - (65/6)*n^4 + (173/6)*n^3 + (148/3)*n^2 - (862/3)*n + 265 : n in [4..40]]; // Wesley Ivan Hurt, Aug 28 2015

(MAGMA) I:=[1, 20, 281, 1357, 4281, 10666]; [n le 6 select I[n] else 6*Self(n-1)-15*Self(n-2)+20*Self(n-3)-15*Self(n-4)+6*Self(n-5)-Self(n-6): n in [1..40]]; // Vincenzo Librandi, Aug 29 2015

CROSSREFS

Sequence in context: A017999 A244653 A012836 * A278360 A019040 A021204

Adjacent sequences:  A028291 A028292 A028293 * A028295 A028296 A028297

KEYWORD

nonn,easy

AUTHOR

R. K. Guy

EXTENSIONS

More terms from David Wasserman, Jan 22 2005

Entry revised by N. J. A. Sloane, Jun 15 2014

STATUS

approved

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Last modified December 3 18:47 EST 2016. Contains 278745 sequences.