A143237 Triangle read by rows, A130208 * A000012 * A130208; 1<=k<=n.

1, 3, 9, 4, 12, 16, 7, 21, 28, 49, 6, 18, 24, 42, 36, 12, 36, 48, 84, 72, 144, 8, 24, 32, 56, 48, 96, 64, 15, 45, 60, 105, 90, 180, 120, 225, 13, 39, 52, 91, 78, 156, 104, 195, 169, 18, 54, 72, 126, 108, 216, 144, 270, 234, 324, 12, 36, 48, 84, 72, 144, 96, 180, 156, 216

Offset

1,2

Comments

Row sums = A143238: (1, 12, 32, 105, 126,...).

Links

Table of n, a(n) for n=1..65.

Formula

Triangle read by rows, A130208 * A000012 * A130208; 1<=k<=n. T(n,k) = sigma(n)*sigma(k), where sigma(n) = A000203, the sum of divisors of n.

Example

First few rows of the triangle =
1;
3, 9;
4, 12, 16;
7, 21, 28, 49;
6, 18, 24, 42, 36;
12, 36, 48, 84, 72, 144;
8, 24, 32, 56, 48, 96, 64;
15, 45, 60, 105, 90, 180, 120, 225;
13, 39, 52, 91, 78, 156, 104, 195, 169;
...
T(6,3) = 48 = sigma(6)*sigma(3) = 12*4

Crossrefs

Cf. A000203, A024916, A130208, A143238.

Sequence in context: A249414 A011428 A070356 * A180485 A370464 A357254

Adjacent sequences: A143234 A143235 A143236 * A143238 A143239 A143240

Keyword

nonn,tabl

Author

Gary W. Adamson, Aug 01 2008

Status

approved