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A154720 Triangle read by rows in which row n lists 2n-1 terms: n, in the center of the row and all the pairs of noncomposite numbers equidistant to n, with 0's inserted, as shown below in the example. 20
1, 1, 2, 3, 1, 0, 3, 0, 5, 1, 0, 3, 4, 5, 0, 7, 0, 0, 3, 0, 5, 0, 7, 0, 0, 1, 0, 0, 0, 5, 6, 7, 0, 0, 0, 11, 1, 0, 3, 0, 0, 0, 7, 0, 0, 0, 11, 0, 13, 0, 0, 3, 0, 5, 0, 0, 8, 0, 0, 11, 0, 13, 0, 0, 1, 0, 0, 0, 5, 0, 7, 0, 9, 0, 11, 0, 13, 0, 0, 0, 17 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 1..10000

EXAMPLE

Triangle begins:

                           1

                        1  2  3

                     1  0  3  0  5

                  1  0  3  4  5  0  7

               0  0  3  0  5  0  7  0  0

            1  0  0  0  5  6  7  0  0  0 11

         1  0  3  0  0  0  7  0  0  0 11  0 13

      0  0  3  0  5  0  0  8  0  0 11  0 13  0  0

   1  0  0  0  5  0  7  0  9  0 11  0 13  0  0  0 17

1  0  3  0  0  0  7  0  0 10  0  0 13  0  0  0 17  0 19

MAPLE

isnotcomp:=proc(n)return (n=1 or isprime(n)) end:

for n from 1 to 10 do for k from 1 to 2*n-1 do if(k=n or (isnotcomp(k) and isnotcomp(2*n-k)))then print(k):else print(0):fi:od:od: # Nathaniel Johnston, Apr 18 2011

CROSSREFS

Cf. A000040, A008578, A154721-A154727.

Sequence in context: A253580 A020921 A293113 * A071501 A004572 A082839

Adjacent sequences:  A154717 A154718 A154719 * A154721 A154722 A154723

KEYWORD

easy,nonn,tabf

AUTHOR

Omar E. Pol, Jan 14 2009

STATUS

approved

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Last modified July 22 20:51 EDT 2019. Contains 325226 sequences. (Running on oeis4.)