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A294129

Numbers n for which exactly one length minimal language exists having exactly n nonempty words over a countably infinite alphabet such that within each prefix of a word every letter of the alphabet is at least as frequent as the subsequent alphabet letter.

0, 1, 3, 7, 17, 43, 119, 351, 1115, 3735, 13231, 48927, 189079, 757583, 3148063, 13497599, 59704335, 271503647, 1268817471, 6078518911, 29837183007, 149789875903, 768674514815, 4026518397439, 21518708975039, 117199152735615, 650184360936191, 3670861106911743

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OFFSET

1,3

COMMENTS

Numbers n such that A291057(n) equals 1.

Numbers n such that the smallest nonzero term in column n of A293815 equals 1.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..800

FORMULA

a(n) = a(n-1) + A000085(n-1) for n>1, a(1) = 0.

a(n) = 2*a(n-1)+(n-3)*a(n-2)-(n-2)*a(n-3) for n>= 4, a(n) = n*(n-1)/2 for n<4.

a(n) = A245176(n-1) - 1 for n>0.