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A089264 Number of permutations of length n containing exactly once 132 and 213, likewise for pattern pair (231,312). 1
3, 6, 17, 42, 102, 242, 564, 1296, 2944, 6624, 14784, 32768, 72192, 158208, 345088, 749568, 1622016, 3497984, 7520256, 16121856, 34471936, 73531392, 156499968, 332398592, 704643072, 1491075072, 3149922304, 6643777536, 13992198144 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,1

LINKS

Table of n, a(n) for n=4..32.

A. Robertson, Permutations restricted by two distinct patterns of length three

Index entries for linear recurrences with constant coefficients, signature (6,-12,8).

FORMULA

For n>=7, (n^2+21*n-28)*2^(n-9).

G.f.: x^4*(x-1)^2*(2*x^3-2*x^2+6*x-3) / (2*x-1)^3. [Colin Barker, Jan 31 2013]

CROSSREFS

Cf. A001815.

Sequence in context: A297972 A275057 A320807 * A121399 A212421 A238428

Adjacent sequences:  A089261 A089262 A089263 * A089265 A089266 A089267

KEYWORD

nonn,easy

AUTHOR

Ralf Stephan, Oct 30 2003

STATUS

approved

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Last modified June 12 14:45 EDT 2021. Contains 344957 sequences. (Running on oeis4.)