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A128089 Denominators in inverse of triangle A128078 By rows, n * each term in n-th row of A126615. 1
1, 4, 4, 6, 18, 9, 8, 24, 48, 16, 10, 30, 60, 100, 25, 12, 36, 72, 120, 180, 36, 14, 42, 84, 140, 210, 294, 49, 16, 48, 96, 160, 240, 336, 448, 64, 18, 54, 108, 180, 270, 378, 504, 648, 81, 20, 60, 120, 200, 300, 420, 560, 720, 900, 100 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row sums = A014820: (1, 8, 33, 96, 225, 456,...) A128089 = denominators of the inverse of A128078: (1/1; 1/4, 1/4; 1/6, 1/18, 1/9; 1/8, 1/24, 1/48, 1/16;...). Row sums of this triangle = 1/1, 1/2, 1/3,...; e.g. (1/8 + 1/24 + 1/48 + 1/16) = 1/4.

LINKS

Table of n, a(n) for n=1..55.

FORMULA

Denominators in inverse triangular matrix of A128078, where A128078 = A002260 * A128064, = (1; -1, 4; -1, -2, 9; -1, -2, -3, 16;...).

EXAMPLE

First few rows of the triangle are:

1;

4, 4;

6, 18, 9;

8, 24, 48, 16;

10, 30, 60, 100, 25;

12, 36, 72, 120, 180, 36;

14, 42, 84, 140, 210, 294, 49;

16, 48, 96, 160, 240, 336, 448, 64;

...

Row 4 = (8, 24, 48, 16) = 4 * (2, 6, 12, 4); where (2, 6, 12, 4) = row 4 of A126615.

CROSSREFS

Cf. A128078, A014820, A006527, A126615, A002260, A128064.

Sequence in context: A078321 A195954 A278532 * A019176 A143391 A158661

Adjacent sequences:  A128086 A128087 A128088 * A128090 A128091 A128092

KEYWORD

nonn,tabl,frac

AUTHOR

Gary W. Adamson, Feb 14 2007

STATUS

approved

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Last modified June 21 12:19 EDT 2021. Contains 345364 sequences. (Running on oeis4.)