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A261840 Number of compositions of n into distinct parts where each part i is marked with a word of length i over a binary alphabet whose letters appear in alphabetical order. 2
1, 2, 3, 16, 21, 50, 205, 292, 587, 1110, 4535, 5980, 12447, 20910, 40195, 142520, 196291, 372042, 635081, 1128872, 1873245, 6537466, 8553639, 16333532, 26470861, 46629886, 73222631, 127947300, 385293581, 518212198, 939401193, 1516760160, 2564361235 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
Also matrices with two rows of nonnegative integers with distinct positive column sums and total element sum n.
LINKS
MAPLE
b:= proc(n, i, p) option remember;
`if`(i*(i+1)/2<n, 0, `if`(n=0, p!, b(n, i-1, p)+
`if`(i>n, 0, b(n-i, i-1, p+1)*(i+1))))
end:
a:= n-> b(n$2, 0):
seq(a(n), n=0..40);
CROSSREFS
Column k=2 of A261835.
Sequence in context: A171458 A044905 A045877 * A100643 A067037 A117926
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Sep 03 2015
STATUS
approved

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Last modified April 20 03:59 EDT 2024. Contains 371798 sequences. (Running on oeis4.)