A286180 - OEIS

A286180

Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of (Product_{j>0} (1 + x^j) * (1 - x^(2*j)))^k in powers of x.

1, 1, 0, 1, 1, 0, 1, 2, 0, 0, 1, 3, 1, 1, 0, 1, 4, 3, 2, 0, 0, 1, 5, 6, 4, 2, 0, 0, 1, 6, 10, 8, 6, 0, 1, 0, 1, 7, 15, 15, 13, 3, 3, 0, 0, 1, 8, 21, 26, 25, 12, 6, 2, 0, 0, 1, 9, 28, 42, 45, 31, 14, 9, 0, 0, 0, 1, 10, 36, 64, 77, 66, 35, 24, 3, 2, 1, 0, 1, 11, 45

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OFFSET

0,8

COMMENTS

A(n, k) is the number of ways of writing n as the sum of k triangular numbers.

LINKS

Seiichi Manyama, Antidiagonals n = 0..139, flattened

FORMULA

G.f. of column k: (Product_{j>0} (1 + x^j) * (1 - x^(2*j)))^k.

EXAMPLE

Square array begins:

1, 1, 1, 1, 1, 1, ...

0, 1, 2, 3, 4, 5, ...

0, 0, 1, 3, 6, 10, ...

0, 1, 2, 4, 8, 15, ...

0, 0, 2, 6, 13, 25, ...

MATHEMATICA

Table[Function[k, SeriesCoefficient[Product[(1 + x^i) (1 - x^(2 i)), {i, Infinity}]^k, {x, 0, n}]][j - n], {j, 0, 12}, {n, 0, j}] // Flatten (* Michael De Vlieger, May 07 2017 *)

CROSSREFS

Columns k=0-12 give A000007, A010054, A008441, A008443, A008438, A008439, A008440, A226252, A007331, A226253, A226254, A226255, A014787.

Main diagonal gives A106337.

Sequence in context: A290975 A367145 A291678 * A291701 A286352 A332898

Adjacent sequences: A286177 A286178 A286179 * A286181 A286182 A286183

KEYWORD

nonn,tabl

AUTHOR

Seiichi Manyama, May 07 2017

STATUS

approved