A128225 A127899 (unsigned) * A004736.

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

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: A069268 A348060 A082155 * A136398 A376729 A228692

Adjacent sequences: A128222 A128223 A128224 * A128226 A128227 A128228

Keyword

nonn,tabl

Author

Gary W. Adamson, Feb 19 2007

Status

approved