A154721 Triangle read by rows in which row n lists 2n-1 terms: The pairs of noncomposite numbers equidistant to n, with 0's inserted, as shown below in the example.

0, 1, 0, 3, 1, 0, 0, 0, 5, 1, 0, 3, 0, 5, 0, 7, 0, 0, 3, 0, 0, 0, 7, 0, 0, 1, 0, 0, 0, 5, 0, 7, 0, 0, 0, 11, 1, 0, 3, 0, 0, 0, 0, 0, 0, 0, 11, 0, 13, 0, 0, 3, 0, 5, 0, 0, 0, 0, 0, 11, 0, 13, 0, 0, 1, 0, 0, 0, 5, 0, 7, 0, 0, 0, 11, 0, 13, 0, 0, 0, 17

Offset

1,4

Links

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

Example

Triangle begins:
                           0
                        1  0  3
                     1  0  0  0  5
                  1  0  3  0  5  0  7
               0  0  3  0  0  0  7  0  0
            1  0  0  0  5  0  7  0  0  0 11
         1  0  3  0  0  0  0  0  0  0 11  0 13
      0  0  3  0  5  0  0  0  0  0 11  0 13  0  0
   1  0  0  0  5  0  7  0  0  0 11  0 13  0  0  0 17
1  0  3  0  0  0  7  0  0  0  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(not k=n and (isnotcomp(k) and isnotcomp(2*n-k)))then print(k):else print(0):fi:od:od: # Nathaniel Johnston, Apr 18 2011

Mathematica

T[n_, k_] := If[k != n && !CompositeQ[k] && !CompositeQ[2n - k], k, 0];
Table[T[n, k], {n, 1, 10}, {k, 1, 2n - 1}] // Flatten (* Jean-François Alcover, Dec 04 2017 *)

Crossrefs

Cf. A000040, A008578, A154720, A154722, A154723, A154724, A154725, A154726, A154727.

Sequence in context: A099725 A285118 A128208 * A350449 A185664 A300812

Adjacent sequences: A154718 A154719 A154720 * A154722 A154723 A154724

Keyword

easy,nonn,tabf

Author

Omar E. Pol, Jan 14 2009

Status

approved