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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
OFFSET
1,4
LINKS
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 *)
KEYWORD
easy,nonn,tabf
AUTHOR
Omar E. Pol, Jan 14 2009
STATUS
approved