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A109673 Hexagonal pyramid related to Prouhet-Tarry problem. 6
1, 1, 1, 1, 3, 1, 1, 1, 1, 2, 1, 2, 8, 8, 2, 1, 8, 15, 8, 1, 2, 8, 8, 2, 1, 2, 1, 1, 3, 3, 1, 3, 15, 24, 15, 3, 3, 24, 60, 60, 24, 3, 1, 15, 60, 93, 60, 15, 1, 3, 24, 60, 60, 24, 3, 3, 15, 24, 15, 3, 1, 3, 3, 1, 1, 4, 6, 4, 1, 4, 24, 52, 52, 24, 4, 6, 52, 160, 228, 160, 52, 6, 4, 52 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Entries of slices [n,n] in A109672, read by rows.

Greatest numbers in each slice (central numbers) form A002893 : 1, 3, 15, 93, 639, ...

LINKS

Table of n, a(n) for n=0..83.

FORMULA

Sum of terms in slice [n, n] = 3^(2n); example : 1+2+1+2+8+15+8+1+2+8+8+2+1+2+1 = 3^4 = 81 for the slice [2, 2].

EXAMPLE

Slice [0, 0]:

... 1 ...

Slice [1,1]:

... 1 1 ...

.. 1 3 1 ...

... 1 1 ...

Slice [2,2]:

.... 1 2 1 ...

... 2 8 8 2 ...

.. 1 8 15 8 1 ...

... 2 8 8 2 ...

.... 1 2 1 ....

Slice [3,3]:

...... 1 3 3 1 .....

.... 3 15 24 15 3 ...

... 3 24 60 60 24 3 ...

.. 1 15 60 93 60 15 1 ...

... 3 24 60 60 24 3 ...

.... 3 15 24 15 3 ....

...... 1 3 3 1 ....

CROSSREFS

Sequence in context: A109393 A030348 A143811 * A023591 A165661 A107711

Adjacent sequences:  A109670 A109671 A109672 * A109674 A109675 A109676

KEYWORD

nonn,tabf,easy

AUTHOR

Philippe Deléham, Aug 07 2005

STATUS

approved

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Last modified June 6 14:04 EDT 2020. Contains 334827 sequences. (Running on oeis4.)