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A128225 A127899 (unsigned) * A004736. 2
1, 6, 2, 15, 9, 3, 28, 20, 12, 4, 45, 35, 25, 15, 5, 66, 54, 42, 30, 18, 6, 91, 77, 63, 49, 35, 21, 7, 120, 104, 88, 72, 56, 40, 24, 8, 153, 135, 117, 99, 81, 63, 45, 27, 9, 190, 170, 150, 130, 110, 90, 70, 50, 30, 10 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row sums = the cubes, A000578: (1, 8, 27, 64, 125, ...). Left column = the hexagonal numbers: A000384: (1, 6, 15, 28, ...). A128226 = A004736 * A127899.

LINKS

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

FORMULA

A127899 (unsigned) * A004736, as infinite lower triangular matrices. Triangle read by rows: n*[(1); (3,1); (5,3,1);...]; cf. A099375.

EXAMPLE

First few rows of the triangle are:

   1;

   6,  2;

  15,  9,  3;

  28, 20, 12,  4;

  45, 35, 25, 15,  5;

  66, 54, 42, 30, 18,  6;

  91, 77, 63, 49, 35, 21,  7;

  ...

MATHEMATICA

(* a127899U computes the unsigned version of A127899 *)

a127899U[n_, k_] := If[n==k||n-1==k, n, 0]/; (1<=k<=n)

a004736[n_, k_] := n-k+1/; (1<=k<=n+1)

a128225[n_, k_] := a127899U[n, n](a004736[n, k] + a004736[n-1, k])/; (1<=k<=n)

a128225[r_] := Table[a128225[n, k], {n, 1, r}, {k, 1, n}]

TableForm[a128225[7]] (* triangle *)

Flatten[a128225[10]] (* data *) (* Hartmut F. W. Hoft, Mar 13 2017 *)

CROSSREFS

Cf. A000384, A000578, A004736, A099375, A127899, A128226.

Sequence in context: A116420 A069268 A082155 * A136398 A228692 A213771

Adjacent sequences:  A128222 A128223 A128224 * A128226 A128227 A128228

KEYWORD

nonn,tabl

AUTHOR

Gary W. Adamson, Feb 19 2007

STATUS

approved

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Last modified July 22 16:34 EDT 2019. Contains 325224 sequences. (Running on oeis4.)