A340792 List in which n appears ceiling(d(n)/2) = A038548(n) times, where d(n) is the number of divisors of n.

1, 2, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 9, 10, 10, 11, 12, 12, 12, 13, 14, 14, 15, 15, 16, 16, 16, 17, 18, 18, 18, 19, 20, 20, 20, 21, 21, 22, 22, 23, 24, 24, 24, 24, 25, 25, 26, 26, 27, 27, 28, 28, 28, 29, 30, 30, 30, 30, 31, 32, 32, 32, 33, 33, 34, 34, 35, 35, 36, 36, 36, 36, 36

Offset: 1

Author

Charles Kusniec, Jan 21 2021

Keywords

• nonn
• tabf

Comments

The numbers in A075362 arranged in numerical order.

Examples

			Array begins:
   1
   2
   3
   4  4
   5
   6  6
   7
   8  8
   9  9
  10 10
  11
  12 12 12
  13
  14 14
  15 15
  16 16 16
  17
  18 18 18
  19
  20 20 20
  21 21
  22 22
  23
  24 24 24 24
		

Links

• Charles Kusniec, Bijection between OEIS sequence A340792 and the positive Triangular Multiplication Table

Crossrefs

Cf. A038548 (row lengths), A075362, A161906, A340791, A061017 (comparable array).

Programs

PARI

row(n) = my(d=divisors(n), r1=select(x->(x<=sqrt(n)), d), r2=Vecrev(select(x->(x>=sqrt(n)), d))); vector(#r1, k, r1[k]*r2[k]); \\ Michel Marcus, Jan 22 2021

Formula

T(n,k) = A161906(n,k) * A340791(n,k).