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A003006 Number of n-level ladder expressions with A001622.
(Formerly M0845)
1
1, 1, 2, 3, 7, 15, 35, 81, 195 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

REFERENCES

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

LINKS

Table of n, a(n) for n=1..9.

R. K. Guy and J. L. Selfridge, The nesting and roosting habits of the laddered parenthesis, Amer. Math. Monthly 80 (8) (1973), 868-876.

R. K. Guy and J. L. Selfridge, The nesting and roosting habits of the laddered parenthesis (annotated cached copy)

Index entries for sequences related to parenthesizing

CROSSREFS

Is this the same as A052321?

Sequence in context: A213920 A248869 A005909 * A052321 A114584 A039826

Adjacent sequences:  A003003 A003004 A003005 * A003007 A003008 A003009

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified January 19 20:01 EST 2019. Contains 319309 sequences. (Running on oeis4.)