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

1,1

Comments

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

Triangle of primes mentioned in A061802.

Links

Table of n, a(n) for n=1..100.

Example

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

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 *)

Crossrefs

Cf. A000040, A061802, A066622, A037126.

Sequence in context: A108939 A370835 A362972 * A285727 A281908 A106441

Adjacent sequences: A138140 A138141 A138142 * A138144 A138145 A138146

Keyword

easy,nonn,tabf

Author

Omar E. Pol, Mar 09 2008

Extensions

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

Status

approved