This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A154725 #22 Aug 16 2025 07:05:01
%S A154725 0,0,0,0,0,0,0,0,0,0,0,3,0,5,0,0,0,0,3,0,0,0,7,0,0,0,0,0,0,5,0,7,0,0,
%T A154725 0,0,0,0,3,0,0,0,0,0,0,0,11,0,0,0,0,3,0,5,0,0,0,0,0,11,0,13,0,0,0,0,0,
%U A154725 0,5,0,7,0,0,0,11,0,13,0,0,0,0
%N A154725 Triangle read by rows in which row n lists 2n-1 terms: The pairs of prime numbers that are equidistant to n, with 0's inserted, as shown below in the example.
%C A154725 Each entry of the n-th row is either 0 or a prime p from the 2n-th row of A002260 such that 2n-p is also prime. - _Jason Kimberley_, Jul 08 2012
%H A154725 Nathaniel Johnston, <a href="/A154725/b154725.txt">Table of n, a(n) for n = 1..10000</a>
%e A154725 Triangle begins:
%e A154725 0
%e A154725 0, 0, 0
%e A154725 0, 0, 0, 0, 0
%e A154725 0, 0, 3, 0, 5, 0, 0
%e A154725 0, 0, 3, 0, 0, 0, 7, 0, 0
%e A154725 0, 0, 0, 0, 5, 0, 7, 0, 0, 0, 0
%e A154725 0, 0, 3, 0, 0, 0, 0, 0, 0, 0,11, 0, 0
%e A154725 0, 0, 3, 0, 5, 0, 0, 0, 0, 0,11, 0,13, 0, 0
%e A154725 0, 0, 0, 0, 5, 0, 7, 0, 0, 0,11, 0,13, 0, 0, 0, 0
%e A154725 0, 0, 3, 0, 0, 0, 7, 0, 0, 0, 0, 0,13, 0, 0, 0,17, 0, 0
%e A154725 From _Jason Kimberley_, Jul 08 2012: (Start)
%e A154725 Square array begins:
%e A154725 3, 3, 3, 0, 3, 3, 0, 3, 3, ...
%e A154725 0, 0, 0, 0, 0, 0, 0, 0, ...
%e A154725 5, 5, 5, 0, 5, 5, 0, 5, ...
%e A154725 0, 0, 0, 0, 0, 0, 0, ...
%e A154725 7, 7, 7, 0, 7, 7, 0, ...
%e A154725 0, 0, 0, 0, 0, 0, ...
%e A154725 0, 0, 0, 0, 0, 0, ...
%e A154725 0, 0, 0, 0, 0, ...
%e A154725 11, 11, 11, 0, 11, ...
%e A154725 0, 0, 0, 0, ...
%e A154725 13, 13, 13, 0, ...
%e A154725 0, 0, 0, ...
%e A154725 0, 0, 0, ...
%e A154725 0, 0, ...
%e A154725 17, 17, ...
%e A154725 0, ...
%e A154725 19, ...
%e A154725 (End)
%p A154725 for n from 1 to 10 do for k from 1 to 2*n-1 do if(not k=n and (isprime(k) and isprime(2*n-k)))then print(k):else print(0):fi:od:od: # _Nathaniel Johnston_, Apr 18 2011
%t A154725 Flatten@Table[If[k != n && PrimeQ[k] && PrimeQ[2 n - k], k, 0], {n, 10}, {k, 2 n - 1}] (* _Robert Price_, Apr 26 2025 *)
%Y A154725 Cf. A000040, A154720, A154721, A154722, A154723, A154724, A154726, A154727.
%K A154725 easy,nonn,tabf
%O A154725 1,12
%A A154725 _Omar E. Pol_, Jan 14 2009