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A154720
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Triangle read by rows in which row n lists 2n-1 terms: n, in the center of the row and all the pairs of noncomposite numbers equidistant to n, with 0's inserted, as shown below in the example.
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20
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1, 1, 2, 3, 1, 0, 3, 0, 5, 1, 0, 3, 4, 5, 0, 7, 0, 0, 3, 0, 5, 0, 7, 0, 0, 1, 0, 0, 0, 5, 6, 7, 0, 0, 0, 11, 1, 0, 3, 0, 0, 0, 7, 0, 0, 0, 11, 0, 13, 0, 0, 3, 0, 5, 0, 0, 8, 0, 0, 11, 0, 13, 0, 0, 1, 0, 0, 0, 5, 0, 7, 0, 9, 0, 11, 0, 13, 0, 0, 0, 17
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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LINKS
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EXAMPLE
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Triangle begins:
1
1 2 3
1 0 3 0 5
1 0 3 4 5 0 7
0 0 3 0 5 0 7 0 0
1 0 0 0 5 6 7 0 0 0 11
1 0 3 0 0 0 7 0 0 0 11 0 13
0 0 3 0 5 0 0 8 0 0 11 0 13 0 0
1 0 0 0 5 0 7 0 9 0 11 0 13 0 0 0 17
1 0 3 0 0 0 7 0 0 10 0 0 13 0 0 0 17 0 19
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MAPLE
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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(k=n or (isnotcomp(k) and isnotcomp(2*n-k)))then print(k):else print(0):fi:od:od: # Nathaniel Johnston, Apr 18 2011
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CROSSREFS
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KEYWORD
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easy,nonn,tabf
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AUTHOR
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STATUS
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approved
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