A138143 Triangle read by rows in which row n lists p(1), p(2), ..., p(n), p(n-1), ..., p(1), where p(i) = i-th prime.

2, 2, 3, 2, 2, 3, 5, 3, 2, 2, 3, 5, 7, 5, 3, 2, 2, 3, 5, 7, 11, 7, 5, 3, 2, 2, 3, 5, 7, 11, 13, 11, 7, 5, 3, 2, 2, 3, 5, 7, 11, 13, 17, 13, 11, 7, 5, 3, 2, 2, 3, 5, 7, 11, 13, 17, 19, 17, 13, 11, 7, 5, 3, 2, 2, 3, 5, 7, 11, 13, 17, 19, 23, 19, 17, 13, 11, 7, 5, 3, 2, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 23, 19, 17, 13, 11, 7, 5, 3, 2

Offset: 1

Author

Omar E. Pol, Mar 09 2008

Keywords

• easy
• nonn
• tabf

Comments

Row n contains 2n-1 terms and each column lists the prime numbers A000040.

Triangle of primes mentioned in A061802.

Examples

			Triangle begins:
.............. 2
........... 2, 3, 2
........ 2, 3, 5, 3, 2
..... 2, 3, 5, 7, 5, 3, 2
.. 2, 3, 5, 7,11, 7, 5, 3, 2
		

Crossrefs

Cf. A000040, A061802, A066622, A037126.

Programs

Mathematica

nn=10;Module[{pr=Prime[Range[nn]],e},Flatten[Table[e=Take[pr,n];Join[ e,Reverse[Most[e]]],{n,nn}]]] (* Harvey P. Dale, Mar 14 2015 *)

Extensions

Edited by N. J. A. Sloane, Apr 07 2008, Nov 15 2008