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A243737 Number of compositions of n with exactly two occurrences of the largest part. 2
1, 0, 1, 3, 7, 13, 25, 46, 89, 175, 351, 710, 1443, 2926, 5920, 11936, 23987, 48072, 96139, 191977, 382992, 763686, 1522581, 3035979, 6055454, 12082887, 24120923, 48174935, 96259627, 192418152, 384772810, 769651514, 1539889604, 3081525905, 6167365392 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,4

LINKS

Joerg Arndt and Alois P. Heinz, Table of n, a(n) for n = 2..650

MAPLE

b:= proc(n, p, i) option remember; `if`(n=0, p!,

      `if`(i<1, 0, add(b(n-i*j, p+j, i-1)/j!, j=0..n/i)))

    end:

a:= proc(n) local k; k:=2;

      add(b(n-i*k, k, i-1)/k!, i=1..n/k)

    end:

seq(a(n), n=2..40);

MATHEMATICA

b[n_, p_, i_] := b[n, p, i] = If[n == 0, p!, If[i<1, 0, Sum[b[n-i*j, p+j, i-1]/j!, {j, 0, n/i}]]]; a[n_] := (k=2; Sum[b[n-i*k, k, i-1]/k!, {i, 1, n/k}]) ; Table[ a[n], {n, 2, 40}] (* Jean-François Alcover, Feb 10 2015, after Maple *)

CROSSREFS

Column k=2 of A238341.

Sequence in context: A259343 A210613 A304648 * A269832 A336726 A201081

Adjacent sequences:  A243734 A243735 A243736 * A243738 A243739 A243740

KEYWORD

nonn

AUTHOR

Joerg Arndt and Alois P. Heinz, Jun 09 2014

STATUS

approved

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Last modified August 8 19:29 EDT 2020. Contains 336298 sequences. (Running on oeis4.)