A138879 - OEIS

A138879

Sum of all parts of the last section of the set of partitions of n.

1, 3, 5, 11, 15, 31, 39, 71, 94, 150, 196, 308, 389, 577, 750, 1056, 1353, 1881, 2380, 3230, 4092, 5412, 6821, 8935, 11150, 14386, 17934, 22834, 28281, 35735, 43982, 55066, 67551, 83821, 102365, 126267, 153397, 188001, 227645, 277305, 334383

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Row sums of the triangles A135010, A138121, A138151 and others related to the section model of partitions (see A135010 and A138121).

From Omar E. Pol, Jan 20 2021: (Start)

Convolution of A000203 and A002865.

Convolution of A340793 and A000041.

Row sums of triangles A339278, A340426, A340583. (End)

a(n) is also the sum of all divisors of all terms of n-th row of A336811. These divisors are also all parts in the last section of the set of partitions of n. - Omar E. Pol, Jul 27 2021

Row sums of A336812. - Omar E. Pol, Aug 03 2021

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A000041(n)*n - A000041(n-1)*(n-1) = A138880(n) + A000041(n-1).

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

a(n) ~ exp(Pi*sqrt(2*n/3)) * Pi/(12*sqrt(2*n)) * (1 - (72 + 13*Pi^2) / (24*Pi*sqrt(6*n)) + (7/12 + 3/(2*Pi^2) + 217*Pi^2/6912)/n - (15*sqrt(3/2)/(16*Pi) + 115*Pi/(288*sqrt(6)) + 4069*Pi^3/(497664*sqrt(6)))/n^(3/2)). - Vaclav Kotesovec, Oct 21 2016, extended Jul 06 2019

G.f.: x*(1 - x)*f'(x), where f(x) = Product_{k>=1} 1/(1 - x^k). - Ilya Gutkovskiy, Apr 13 2017

EXAMPLE

a(6)=31 because the parts of the last section of the set of partitions of 6 are (6), (3,3), (4,2), (2,2,2), (1), (1), (1), (1), (1), (1), (1), so the sum is a(6) = 6 + 3 + 3 + 4 + 2 + 2 + 2 + 2 + 1 + 1 + 1 + 1 + 1 + 1 + 1 = 31.

From Omar E. Pol, Aug 13 2013: (Start)

Illustration of initial terms:

. _ _ _ _ _ _

. |_ _ _ _ _ _|

. |_ _ _|_ _ _|

. |_ _ _ _|_ _|

. _ _ _ _ _ |_ _|_ _|_ _|

. |_ _ _ _ _| |_|

. _ _ _ _ |_ _ _|_ _| |_|

. |_ _ _ _| |_| |_|

. _ _ _ |_ _|_ _| |_| |_|

. _ _ |_ _ _| |_| |_| |_|

. _ |_ _| |_| |_| |_| |_|

. |_| |_| |_| |_| |_| |_|

. 1 3 5 11 15 31

(End)

On the other hand for n = 6 the 6th row of triangle A336811 is [6, 4, 3, 2, 2, 1, 1] and the sum of all divisors of these terms is [1 + 2 + 3 + 6] + [1 + 2 + 4] + [1 + 3] + [1 + 2] + [1 + 2] + [1] + [1] = 31, so a(6) = 31. - Omar E. Pol, Jul 27 2021

MAPLE

A066186 := proc(n) n*combinat[numbpart](n) ; end proc:

A138879 := proc(n) A066186(n)-A066186(n-1) ; end proc:

seq(A138879(n), n=1..80) ; # R. J. Mathar, Jan 27 2011

MATHEMATICA

Table[PartitionsP[n]*n - PartitionsP[n-1]*(n-1), {n, 1, 50}] (* Vaclav Kotesovec, Oct 21 2016 *)

PROG

(PARI) for(n=1, 50, print1(numbpart(n)*n - numbpart(n - 1)*(n - 1), ", ")) \\ Indranil Ghosh, Mar 19 2017

(Python)

from sympy.ntheory import npartitions

print([npartitions(n)*n - npartitions(n - 1)*(n - 1) for n in range(1, 51)]) # Indranil Ghosh, Mar 19 2017

CROSSREFS

Cf. A000041, A000203, A002865, A066186, A133041, A135010, A138121, A138135 - A138138, A138151, A138880, A139100, A237593, A336811, A336812, A338156, A339278, A340035, A340426, A340583, A340793.

Sequence in context: A164053 A200176 A092929 * A336136 A318915 A322439

Adjacent sequences: A138876 A138877 A138878 * A138880 A138881 A138882

KEYWORD

nonn

AUTHOR

Omar E. Pol, Apr 30 2008

EXTENSIONS

a(34) corrected by R. J. Mathar, Jan 27 2011

STATUS

approved