A143836 - OEIS

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

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OFFSET

1,1

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

LINKS

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

EXAMPLE

Triangle begins:

5, 6;

7, 8, 9;

8, 9, 10, 12;

10, 11, 12, 14, 15;

...

PROG

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

CROSSREFS

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

Sequence in context: A248355 A178053 A090925 * A168094 A367063 A089166

Adjacent sequences: A143833 A143834 A143835 * A143837 A143838 A143839

KEYWORD

nonn,tabl

AUTHOR

Pierre CAMI, Sep 02 2008

EXTENSIONS

Name simplified by Ya-Ping Lu, Mar 05 2023

STATUS

approved