A340526 Triangle read by rows: T(n,k) = A006218(n-k+1)*A000041(k-1), 1 <= k <= n.

1, 3, 1, 5, 3, 2, 8, 5, 6, 3, 10, 8, 10, 9, 5, 14, 10, 16, 15, 15, 7, 16, 14, 20, 24, 25, 21, 11, 20, 16, 28, 30, 40, 35, 33, 15, 23, 20, 32, 42, 50, 56, 55, 45, 22, 27, 23, 40, 48, 70, 70, 88, 75, 66, 30, 29, 27, 46, 60, 80, 98, 110, 120, 110, 90, 42, 35, 29, 54, 69, 100, 112, 154, 150, 176, 150, 126, 56

Offset

1,2

Comments

Conjecture 1: T(n,k) is the total number of divisors of the terms that are in the k-th blocks of the first n rows of triangle A176206.

Conjecture 2: the sum of row n equals A284870, the total number of parts in all partitions of all positive integers <= n.

The above conjectures are connected due to the correspondence between divisors and partitions (cf. A336811).

Links

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

Example

Triangle begins:
   1;
   3,  1;
   5,  3,  2;
   8,  5,  6,  3;
  10,  8, 10,  9,   5;
  14, 10, 16, 15,  15,   7;
  16, 14, 20, 24,  25,  21,  11;
  20, 16, 28, 30,  40,  35,  33,  15;
  23, 20, 32, 42,  50,  56,  55,  45,  22;
  27, 23, 40, 48,  70,  70,  88,  75,  66,  30;
  29, 27, 46, 60,  80,  98, 110, 120, 110,  90,  42;
  35, 29, 54, 69, 100, 112, 154, 150, 176, 150, 126,  56;
...
For n = 6 the calculation of every term of row 6 is as follows:
--------------------------
k   A000041         T(6,k)
1      1  *  14   =   14
2      1  *  10   =   10
3      2  *   8   =   16
4      3  *   5   =   15
5      5  *   3   =   15
6      7  *   1   =    7
.          A006218
--------------------------
The sum of row 6 is 14 + 10 + 16 + 15 + 15 + 7 = 77, equaling A284870(6).

Prog

(PARI) f(n) = sum(k=1, n, n\k); \\ A006218
T(n, k) = f(n-k+1)*numbpart(k-1); \\ Michel Marcus, Jan 15 2021

Crossrefs

Columns 1 and 2 give A006218.

Leading diagonal gives A000041.

Row sums give A284870.

Cf. A176206, A221531, A339106, A340424, A340425, A340524, A340426, A340527, A336811.

Sequence in context: A249100 A356255 A152203 * A161946 A013597 A092131

Adjacent sequences: A340523 A340524 A340525 * A340527 A340528 A340529

Keyword

nonn,tabl

Author

Omar E. Pol, Jan 10 2021

Status

approved