A131241 - OEIS

A131241

3*A046854 - 2*I.

1, 3, 1, 3, 3, 1, 3, 6, 3, 1, 3, 6, 9, 3, 1, 3, 9, 9, 12, 3, 1, 3, 9, 18, 12, 15, 3, 1, 3, 12, 18, 30, 15, 18, 3, 1, 3, 12, 30, 30, 45, 18, 21, 3, 1, 3, 15, 30, 60, 45, 63, 21, 24, 3, 1

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OFFSET

0,2

COMMENTS

Row sums = A111314: (1, 4, 7, 13, 22, 37, ...). A131240 = 2*A046854 - I.

LINKS

Table of n, a(n) for n=0..54.

FORMULA

3*A046854 - 2*I, where A046854 = Pascal's triangle with repeats by columns and I = Identity matrix.

EXAMPLE

First few rows of the triangle:

3, 1;

3, 3, 1;

3, 6, 3, 1;

3, 6, 9, 3, 1;

3, 9, 9, 12, 3, 1

3, 9, 18, 12, 15, 3, 1;

...

CROSSREFS

Cf. A046854, A111314, A131240.

Sequence in context: A050141 A274773 A132752 * A133599 A256399 A336575

Adjacent sequences: A131238 A131239 A131240 * A131242 A131243 A131244

KEYWORD

nonn,tabl

AUTHOR

Gary W. Adamson, Jun 21 2007

STATUS

approved