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A145547

Number of distinct values taken by 7^7^...^7 (with n 7's and parentheses inserted in all possible ways).

15

1, 1, 2, 4, 9, 20, 48, 115, 286, 719, 1841, 4762, 12470, 32918, 87628, 234795, 633000, 1715435, 4671098, 12772707, 35059815, 96567161, 266818396, 739344427

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..24.

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

Index entries for sequences related to parenthesizing

CROSSREFS

Cf. A002845, A003018, A003019, A145545, A145546, A145548, A145549, A145550, A000081.

Sequence in context: A255639 A216062 A034826 * A292554 A318803 A318856

Adjacent sequences: A145544 A145545 A145546 * A145548 A145549 A145550

KEYWORD

more,nonn

AUTHOR

Jon E. Schoenfield, Oct 13 2008

STATUS

approved