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A138139 Triangle read by rows: row n contains n terms and each column lists the prime numbers A000040.

%I A138139 #7 Feb 06 2019 02:00:51
%S A138139 2,2,2,2,3,2,2,3,3,2,2,3,5,3,2,2,3,5,5,3,2,2,3,5,7,5,3,2,2,3,5,7,7,5,
%T A138139 3,2,2,3,5,7,11,7,5,3,2,2,3,5,7,11,11,7,5,3,2,2,3,5,7,11,13,11,7,5,3,
%U A138139 2,2,3,5,7,11,13,13,11,7,5,3,2,2,3,5,7,11
%N A138139 Triangle read by rows: row n contains n terms and each column lists the prime numbers A000040.
%H A138139 Nathaniel Johnston, <a href="/A138139/b138139.txt">Table of n, a(n) for n = 1..10000</a>
%e A138139 Triangle begins:
%e A138139       2
%e A138139      2,2
%e A138139     2,3,2
%e A138139    2,3,3,2
%e A138139   2,3,5,3,2
%p A138139 A138139 := proc(n,k) return ithprime(min(k,n-k+1)): end: seq(seq(A138139(n,k), k=1..n), n=1..13); # _Nathaniel Johnston_, Apr 30 2011
%Y A138139 Cf. A000040, A003983.
%K A138139 easy,nonn,tabl
%O A138139 1,1
%A A138139 _Omar E. Pol_, Mar 09 2008, Mar 25 2008