A092284 Number of nonterminal symbols in a certain "divide-and-conquer" context-free grammar in Chomsky normal form that generates all permutations of n symbols.

1, 3, 7, 11, 26, 42, 99, 107, 382, 428, 1156, 1223, 4525, 4903, 14811, 14827, 58022, 61236, 201420, 201611

Offset

1,2

Links

Table of n, a(n) for n=1..20.

P. R. J. Asveld, Generating all permutations by context-free grammars in Chomsky normal form, Theoretical Computer Science 354 (2006) 118-130.

Formula

a(n) = Sum_{k=1..n} t(n, k), where t(n, k) is the n-th row of the Pascal-like triangle of A090349.

Example

a(4) = 4 + 6 + 0 + 1 = 11; cf. the example grammar of A090349.

Crossrefs

Cf. A090349.

Sequence in context: A336897 A316962 A360297 * A024459 A001645 A103798

Adjacent sequences: A092281 A092282 A092283 * A092285 A092286 A092287

Keyword

nonn,more

Author

Peter R. J. Asveld, Jan 30 2004

Status

approved