A103218 - OEIS

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A103218

Triangle read by rows: T(n, k) = (2*k+1)*(n+1-k)^2.

1, 4, 3, 9, 12, 5, 16, 27, 20, 7, 25, 48, 45, 28, 9, 36, 75, 80, 63, 36, 11, 49, 108, 125, 112, 81, 44, 13, 64, 147, 180, 175, 144, 99, 52, 15, 81, 192, 245, 252, 225, 176, 117, 60, 17, 100, 243, 320, 343, 324, 275, 208, 135, 68, 19, 121, 300, 405, 448, 441, 396, 325, 240

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OFFSET

0,2

COMMENTS

The triangle is generated from the product A * B of the infinite lower triangular matrix A =

1 0 0 0...

3 1 0 0...

5 3 1 0...

7 5 3 1...

... and B =

1 0 0 0...

1 3 0 0...

1 3 5 0...

1 3 5 7...

...

LINKS

Table of n, a(n) for n=0..62.

EXAMPLE

Triangle begins:

4,3,

9,12,5,

16,27,20,7,

25,48,45,28,9,

MATHEMATICA

T[n_, k_] := (2*k + 1)*(n + 1 - k)^2; Flatten[ Table[ T[n, k], {n, 0, 10}, {k, 0, n}]] (* Robert G. Wilson v, Feb 10 2005 *)

PROG

(PARI) T(n, k) = (2*k+1)*(n+1-k)^2; for(i=0, 10, for(j=0, i, print1(T(i, j), ", ")); print())

CROSSREFS

Row sums give A002412 (hexagonal pyramidal numbers).

T(n, 0)=A000290(n+1) (the squares);

T(n, 1)=3*n^2=A033428(n);

T(n, 2)=5*n^2=A033429(n+1);

T(n, 3)=7*n^2=A033582(n+2);

Cf. A103219 (product B*A), A002412, A000290.

Sequence in context: A131805 A197694 A187770 * A319311 A107381 A242531

Adjacent sequences: A103215 A103216 A103217 * A103219 A103220 A103221

KEYWORD

nonn,tabl

AUTHOR

Lambert Klasen (lambert.klasen(AT)gmx.de) and Gary W. Adamson, Jan 25 2005

STATUS

approved