A154726 Triangle read by rows in which row n lists: n, in the center of the row and the pairs of prime numbers that are equidistant to n, as shown below in the example.

1, 2, 3, 3, 4, 5, 3, 5, 7, 5, 6, 7, 3, 7, 11, 3, 5, 8, 11, 13, 5, 7, 9, 11, 13, 3, 7, 10, 13, 17, 3, 5, 11, 17, 19, 5, 7, 11, 12, 13, 17, 19, 3, 7, 13, 19, 23, 5, 11, 14, 17, 23, 7, 11, 13, 15, 17, 19, 23, 3, 13, 16, 19, 29, 3, 5, 11, 17, 23, 29

Offset

1,2

Links

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

Example

Triangle begins:
                       1
                       2
                       3
                    3  4  5
                 3  .  5  .  7
              .  .  5  6  7  .  .
           3  .  .  .  7  .  .  . 11
        3  .  5  .  .  8  .  . 11  . 13
     .  .  5  .  7  .  9  . 11  . 13  .  .
  3  .  .  .  7  .  . 10  .  . 13  .  .  . 17

Maple

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

Mathematica

Select[Flatten@Table[If[k == n  || ( PrimeQ[k] && PrimeQ[2 n - k]), k, 0], {n, 10}, {k, 2 n - 1}] , # > 0 &] (* Robert Price, Apr 26 2025 *)

Crossrefs

Cf. A000040, A154720, A154721, A154722, A154723, A154724, A154725, A154727.

Sequence in context: A131282 A305296 A114544 * A325784 A244929 A302920

Adjacent sequences: A154723 A154724 A154725 * A154727 A154728 A154729

Keyword

easy,nonn,tabf

Author

Omar E. Pol, Jan 14 2009

Extensions

a(31)-a(70) from Nathaniel Johnston, Apr 18 2011

Status

approved