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 A154721 Triangle read by rows in which row n lists 2n-1 terms: The pairs of noncomposite numbers equidistant to n, with 0's inserted, as shown below in the example. 17
 0, 1, 0, 3, 1, 0, 0, 0, 5, 1, 0, 3, 0, 5, 0, 7, 0, 0, 3, 0, 0, 0, 7, 0, 0, 1, 0, 0, 0, 5, 0, 7, 0, 0, 0, 11, 1, 0, 3, 0, 0, 0, 0, 0, 0, 0, 11, 0, 13, 0, 0, 3, 0, 5, 0, 0, 0, 0, 0, 11, 0, 13, 0, 0, 1, 0, 0, 0, 5, 0, 7, 0, 0, 0, 11, 0, 13, 0, 0, 0, 17 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS Nathaniel Johnston, Table of n, a(n) for n = 1..10000 EXAMPLE Triangle begins:                            0                         1  0  3                      1  0  0  0  5                   1  0  3  0  5  0  7                0  0  3  0  0  0  7  0  0             1  0  0  0  5  0  7  0  0  0 11          1  0  3  0  0  0  0  0  0  0 11  0 13       0  0  3  0  5  0  0  0  0  0 11  0 13  0  0    1  0  0  0  5  0  7  0  0  0 11  0 13  0  0  0 17 1  0  3  0  0  0  7  0  0  0  0  0 13  0  0  0 17  0 19 MAPLE isnotcomp:=proc(n)return (n=1 or isprime(n)) end: for n from 1 to 10 do for k from 1 to 2*n-1 do if(not k=n and (isnotcomp(k) and isnotcomp(2*n-k)))then print(k):else print(0):fi:od:od: # Nathaniel Johnston, Apr 18 2011 MATHEMATICA T[n_, k_] := If[k != n && !CompositeQ[k] && !CompositeQ[2n - k], k, 0]; Table[T[n, k], {n, 1, 10}, {k, 1, 2n - 1}] // Flatten (* Jean-François Alcover, Dec 04 2017 *) CROSSREFS Cf. A000040, A008578, A154720, A154722, A154723, A154724, A154725, A154726, A154727. Sequence in context: A099725 A285118 A128208 * A185664 A300812 A144209 Adjacent sequences:  A154718 A154719 A154720 * A154722 A154723 A154724 KEYWORD easy,nonn,tabf AUTHOR Omar E. Pol, Jan 14 2009 STATUS approved

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Last modified September 21 00:17 EDT 2019. Contains 327252 sequences. (Running on oeis4.)