A143271 Triangle read by rows: A130209 * A000012 * A127648.

1, 2, 4, 2, 4, 6, 3, 6, 9, 12, 2, 4, 6, 8, 10, 4, 8, 12, 16, 20, 24, 2, 4, 6, 8, 10, 12, 14, 4, 8, 12, 16, 20, 24, 28, 32, 3, 6, 9, 12, 15, 18, 21, 24, 27, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72

Offset

1,2

Comments

Row sums = A143272: (1, 6, 12, 30, 30, 84, 56, ...).

Left border = A000005: (1, 2, 2, 3, 2, 4, 2, 4, 3, ...).

Links

Table of n, a(n) for n=1..78.

Formula

T(n,k) = d(n)*k.

Example

First few rows of the triangle =
  1;
  2, 4;
  2, 4,  6;
  3, 6,  9, 12;
  2, 4,  6,  8, 10;
  4, 8, 12, 16, 20, 24;
  2, 4,  6,  8, 10, 12, 14;
  ...
T(5,3) = 6 = 2*3 = d(5)*3.

Prog

(PARI) tabl(nn) = for (n=1, nn, for (k=1, n, print1(numdiv(n)*k, ", "))); \\ Michel Marcus, Jun 05 2023

Crossrefs

Cf. A000005, A127648, A130209, A143272.

Sequence in context: A214781 A214850 A236186 * A267654 A128859 A047975

Adjacent sequences: A143268 A143269 A143270 * A143272 A143273 A143274

Keyword

nonn,tabl

Author

Gary W. Adamson, Aug 03 2008

Extensions

a(62) corrected by Georg Fischer, Jun 05 2023

Status

approved