

A173997


Irregular triangular by columns derived from (1, 2, 3,...) * (1, 2, 3,...).


2



1, 2, 3, 2, 4, 4, 5, 6, 3, 6, 8, 6, 7, 10, 9, 4, 8, 12, 12, 8, 9, 14, 15, 12, 5, 10, 16, 18, 16, 10, 11, 18, 21, 20, 15, 6, 12, 20, 24, 24, 20, 12
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OFFSET

1,2


COMMENTS

Row sums = A006918: (1, 2, 5, 8, 14, 20, 30,...).


LINKS

Table of n, a(n) for n=1..42.


FORMULA

Given a (1, 2, 3,...) * (1, 2, 3,...) multiplication table; leftmost column
of the triangle = (1, 2, 3,...). Then shift down each successive column of
the array twice to get triangle A173997.


EXAMPLE

Given:
...
1,..2,..3,..4,..5,...
2,..4,..6,..8,.10,...
3,..6,..9,.12,.15,...
4,..8,.12,.16,.20,...
...
After the shift twice operation, we obtain:
...
1;
2;
3, 2;
4, 4;
5, 6, 3;
6, 8, 6;
7, 10, 9, 4;
8, 12, 12, 8;
9, 14, 15, 12, 5;
10, 16, 18, 16, 10;
11, 18, 21, 20, 15, 6;
12, 20, 24, 24, 20, 12;
...


CROSSREFS

Cf. A006918
Sequence in context: A145394 A179806 A182762 * A029143 A153846 A284383
Adjacent sequences: A173994 A173995 A173996 * A173998 A173999 A174000


KEYWORD

nonn,tabf


AUTHOR

Gary W. Adamson, Mar 05 2010


STATUS

approved



