A229936 - OEIS

A229936

Sum of all parts of all compositions of n with at least two parts in increasing order.

0, 0, 0, 3, 12, 45, 126, 343, 848, 2034, 4700, 10648, 23652, 51935, 112798, 243120, 520592, 1109063, 2352366, 4971426, 10473220, 22003464, 46115300, 96440127, 201288792, 419381450, 872351896, 1811858058, 3757992280, 7784495839, 16105959240, 33285784442

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OFFSET

0,4

COMMENTS

Sum of all parts of all compositions of n that are not partitions of n (see example).

LINKS

Table of n, a(n) for n=0..31.

FORMULA

a(n) = n*A056823(n) = n*(A011782(n) - A000041(n)).

a(n) = A001787(n) - A066186(n), n >= 1.

EXAMPLE

For n = 4 the table shows both the compositions and the partitions of 4. There are three compositions of 4 that are not partitions of 4.

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Compositions Partitions Sum of all parts

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[1, 1, 1, 1] = [1, 1, 1, 1]

[2, 1, 1] = [2, 1, 1]

[1, 2, 1] 4

[3, 1] = [3, 1]

[1, 1, 2] 4

[2, 2] = [2, 2]

[1, 3] 4

[4] = [4]

----------------------------------------------------

Total 12

A partition of a positive integer n is any nonincreasing sequence of positive integers which sum to n, ence the compositions of 4 that are not partitions of 4 are [1, 2, 1], [1, 1, 2] and [1, 3]. The sum of all parts of these compositions is 1+3+1+2+1+1+1+2 = 3*4 = 12. On the other hand the sum of all parts in all compositions of 4 is A001787(4) = 32, and the sum of all parts in all partitions of 4 is A066186(4) = 20, so a(4) = 32 - 20 = 12.

CROSSREFS

Cf. A000041, A001787, A011782, A056823, A066186, A229935.

Sequence in context: A005656 A339066 A260146 * A258626 A064017 A005320

Adjacent sequences: A229933 A229934 A229935 * A229937 A229938 A229939

KEYWORD

nonn

AUTHOR

Omar E. Pol, Oct 14 2013

STATUS

approved