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A001268 One-half the number of permutations of length n with exactly 4 rising or falling successions.
(Formerly M4805 N2053)
5
0, 0, 0, 0, 0, 1, 11, 113, 1099, 11060, 118484, 1366134, 16970322, 226574211, 3240161105, 49453685911, 802790789101, 13815657556958, 251309386257874, 4818622686395380, 97145520138758844, 2054507019515346789, 45484006970415223287, 1052036480881734378541 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,7

COMMENTS

(1/2) times number of permutations of 12...n such that exactly 4 of the following occur: 12, 23, ..., (n-1)n, 21, 32, ..., n(n-1).

REFERENCES

F. N. David, M. G. Kendall and D. E. Barton, Symmetric Function and Allied Tables, Cambridge, 1966, p. 263.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..200

J. Riordan, A recurrence for permutations without rising or falling successions, Ann. Math. Statist. 36 (1965), 708-710.

FORMULA

Coefficient of t^4 in S[n](t) defined in A002464, divided by 2.

Recurrence (for n>5): (n-5)*(n^8 - 41*n^7 + 730*n^6 - 7358*n^5 + 45799*n^4 - 179702*n^3 + 432498*n^2 - 581244*n + 332100)*a(n) = (n^10 - 45*n^9 + 895*n^8 - 10301*n^7 + 75340*n^6 - 361190*n^5 + 1124682*n^4 - 2150033*n^3 + 2147364*n^2 - 499899*n - 544266)*a(n-1) - (n^10 - 44*n^9 + 869*n^8 - 10112*n^7 + 76390*n^6 - 388742*n^5 + 1336932*n^4 - 3028095*n^3 + 4237931*n^2 - 3198426*n + 917988)*a(n-2) - (n^10 - 43*n^9 + 823*n^8 - 9195*n^7 + 66108*n^6 - 318138*n^5 + 1033118*n^4 - 2224673*n^3 + 3023402*n^2 - 2325285*n + 761190)*a(n-3) + (n^8 - 33*n^7 + 471*n^6 - 3783*n^5 + 18594*n^4 - 56865*n^3 + 104723*n^2 - 104847*n + 42783)*(n-2)^2*a(n-4). - Vaclav Kotesovec, Aug 11 2013

a(n) ~ n!*exp(-2)/3. - Vaclav Kotesovec, Aug 11 2013

MAPLE

S:= proc(n) option remember; `if`(n<4, [1, 1, 2*t, 4*t+2*t^2]

       [n+1], expand((n+1-t)*S(n-1) -(1-t)*(n-2+3*t)*S(n-2)

       -(1-t)^2*(n-5+t)*S(n-3) +(1-t)^3*(n-3)*S(n-4)))

    end:

a:= n-> ceil(coeff(S(n), t, 4)/2):

seq(a(n), n=0..25);  # Alois P. Heinz, Jan 11 2013

MATHEMATICA

S[n_] := S[n] = If[n<4, {1, 1, 2*t, 4*t + 2*t^2}[[n+1]], Expand[(n+1-t)*S[n-1] - (1-t)*(n-2+3*t)*S[n-2] - (1-t)^2*(n-5+t)*S[n-3] + (1-t)^3*(n-3)*S[n-4]]]; a[n_] := Ceiling[Coefficient[S[n], t, 4]/2]; Table [a[n], {n, 0, 25}] (* Jean-Fran├žois Alcover, Mar 24 2014, after Alois P. Heinz *)

CROSSREFS

Cf. A002464, A000130, A086852. Equals A086855/2. A diagonal of A010028.

Sequence in context: A166572 A111463 A142483 * A065538 A287837 A276200

Adjacent sequences:  A001265 A001266 A001267 * A001269 A001270 A001271

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified October 22 23:17 EDT 2018. Contains 316518 sequences. (Running on oeis4.)