login
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.
0
1, 3, 7, 11, 26, 42, 99, 107, 382, 428, 1156, 1223, 4525, 4903, 14811, 14827, 58022, 61236, 201420, 201611
OFFSET
1,2
LINKS
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
KEYWORD
nonn,more
AUTHOR
Peter R. J. Asveld, Jan 30 2004
STATUS
approved