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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

Alois P. Heinz, Table of n, a(n) for n = 0..5000

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

Adjacent sequences:  A261837 A261838 A261839 * A261841 A261842 A261843

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Sep 03 2015

STATUS

approved

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Last modified November 11 15:59 EST 2019. Contains 329019 sequences. (Running on oeis4.)