A143836 Triangle read by rows: T(r,c) = (prime(r+2) + prime(c+1))/2.

4, 5, 6, 7, 8, 9, 8, 9, 10, 12, 10, 11, 12, 14, 15, 11, 12, 13, 15, 16, 18, 13, 14, 15, 17, 18, 20, 21, 16, 17, 18, 20, 21, 23, 24, 26, 17, 18, 19, 21, 22, 24, 25, 27, 30, 20, 21, 22, 24, 25, 27, 28, 30, 33, 34, 22, 23, 24, 26, 27, 29, 30, 32, 35, 36, 39, 23, 24, 25, 27, 28, 30, 31, 33, 36, 37, 40, 42

Offset: 1

Author

Pierre CAMI, Sep 02 2008

Keywords

• nonn
• tabl

Comments

The number of appearances of m >= 1 in this sequence is A061357(m). Conjecture: Every integer >= 4 appears at least once in this sequence. - Ya-Ping Lu, Mar 05 2023

The number of composites between 3 and (r+2)-th prime missing from Row 1 through Row r in the triangle is A334810(r+2). - Ya-Ping Lu, Mar 24 2023

Examples

			Triangle begins:
   4;
   5,  6;
   7,  8,  9;
   8,  9, 10, 12;
  10, 11, 12, 14, 15;
  ...
		

Crossrefs

Cf. A098090 (1st column, except 1st term), A024675 (right diagonal).

Programs

PARI

T(r,c) = (prime(r+2) + prime(c+1))/2; \\ Michel Marcus, Mar 07 2023

Extensions

Name simplified by Ya-Ping Lu, Mar 05 2023