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A205545 Symmetric matrix by antidiagonals:  C(max(3i,3j),min(3i,3j)), i>=0, j>=0. 0
1, 1, 1, 1, 1, 1, 1, 20, 20, 1, 1, 84, 1, 84, 1, 1, 220, 84, 84, 220, 1, 1, 455, 924, 1, 924, 455, 1, 1, 816, 5005, 220, 220, 5005, 816, 1, 1, 1330, 18564, 5005, 1, 5005, 18564, 1330, 1, 1, 2024, 54264, 48620, 455, 455, 48620, 54264, 2024, 1, 1, 2925 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,8

LINKS

Table of n, a(n) for n=1..57.

EXAMPLE

Northwest corner:

1.....20....84....220

20....1.....84....924

84....84....1.....220

455...5005..5005..455

MATHEMATICA

f[i_, j_] := Binomial[Max[3 i - 3, 3 j - 3], Min[3 i - 3, 3 j - 3]]

TableForm[Table[f[i, j], {i, 1, 10}, {j, 1, 10}]]

Flatten[Table[f[i, n + 1 - i], {n, 1, 14}, {i, 1, n}]]

CROSSREFS

Cf. A205456.

Sequence in context: A261307 A172164 A267058 * A087708 A220022 A217517

Adjacent sequences:  A205542 A205543 A205544 * A205546 A205547 A205548

KEYWORD

nonn,tabl

AUTHOR

Clark Kimberling, Jan 28 2012

STATUS

approved

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Last modified October 18 03:25 EDT 2021. Contains 348065 sequences. (Running on oeis4.)