A209918 Tetrahedron in which the n-th slice is also one of the three views of the shell model of partitions of A207380 with n shells.

1, 2, 1, 1, 3, 2, 1, 1, 1, 1, 5, 4, 2, 1, 1, 2, 2, 1, 1, 1, 7, 6, 4, 2, 1, 1, 2, 3, 2, 1, 1, 2, 1, 1, 1

Offset

1,2

Comments

Each slice of the tetrahedron is a triangle, thus the number of elements in the n-th slice is A000217(n). The slices are perpendicular to the slices of A026792. Each element of the n-th slice equals the volume of a column of the shell model of partitions with n shells. The sum of each column of the n-th slice is A000041(n). The sum of all elements of the n-th slice is A066186(n).

It appears that the triangle formed by the first row of each slice gives A058399.

It appears that the triangle formed by the last column of each slice gives A008284 and A058398.

Also consider a vertical rectangle on the infinite square grid with shorter side = n and longer side = p(n) = A000041(n). Each row of rectangle represents a partition of n. Each part of each partition of n is a horizontal rectangle with shorter side = 1 and longer side = k, where k is the size of the part. It appears that T(n,k,j) is also the number of k-th parts of all partitions of n in the j-th column of rectangle.

Links

Table of n, a(n) for n=1..35.

Example

---------------------------------------------------------
Illustration of first five                       A181187
slices of the tetrahedron                        Row sum
---------------------------------------------------------
. 1,                                                1
.    2, 1,                                          3
.       1,                                          1
.          3, 2, 1                                  6
.             1, 1,                                 2
.                1,                                 1
.                   5, 4, 2, 1,                    12
.                      1, 2, 2,                     5
.                         1, 1                      2
.                            1,                     1
.                               7, 6, 4, 2, 1,     20
.                                  1, 2, 3, 2,      8
.                                     1, 1, 2,      4
.                                        1, 1,      2
.                                           1,      1
--------------------------------------------------------
. 1, 2, 2, 3, 3, 3, 5, 5, 5, 5, 7, 7, 7, 7, 7,
.
Note that the 5th slice appears as one of three views of the model in the example section of A207380.

Crossrefs

Row sums give A181187. Column sums give A209656. Main diagonal gives A210765. Another version is A209655.

Cf. A000041, A000217, A002260, A004736, A008284, A026792, A058398, A058399, A066186, A135010, A182703, A182715, A207380.

Sequence in context: A080577 A302246 A209655 * A030312 A030321 A030305

Adjacent sequences: A209915 A209916 A209917 * A209919 A209920 A209921

Keyword

nonn,tabf,more

Author

Omar E. Pol, Mar 26 2012

Status

approved