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A108939
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Triangle read by rows in which row n lists all primes p such that p-1|n.
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2
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2, 2, 3, 2, 2, 3, 5, 2, 2, 3, 7, 2, 2, 3, 5, 2, 2, 3, 11, 2, 2, 3, 5, 7, 13, 2, 2, 3, 2, 2, 3, 5, 17, 2, 2, 3, 7, 19, 2, 2, 3, 5, 11, 2, 2, 3, 23, 2, 2, 3, 5, 7, 13, 2, 2, 3, 2, 2, 3, 5, 29, 2, 2, 3, 7, 11, 31, 2, 2, 3, 5, 17, 2, 2, 3, 2, 2, 3, 5, 7, 13, 19, 37, 2, 2, 3, 2, 2, 3, 5, 11, 41, 2
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OFFSET
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1,1
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COMMENTS
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Row 2n-1 contains only the term 2.
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LINKS
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EXAMPLE
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Row n = 1 : 2 because 1|1.
Row n = 2 : 2, 3 because 1|2 and 2|2.
Row n = 3 : 2 because 1|3.
Row n = 4 : 2, 3, 5 because 1|4, 2|4 and 4|4.
Row n = 5 : 2 because 1|5.
Row n = 6 : 2, 3, 7 because 1|6, 2|6 and 6|6.
Row n = 7 : 2 because 1|7.
Row n = 8 : 2, 3, 5 because 1|8, 2|8 and 4|8.
Row n = 9 : 2 because 1|9.
Row n = 10 : 2, 3, 11 because 1|10, 2|10 and 10|10.
Row n = 11 : 2 because 1|11.
Row n = 12 : 2, 3, 5, 7, 13 because 1|12, 2|12, 4|12, 6|12 = and 12|12.
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MAPLE
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with(numtheory): for n from 1 to 20 do div:=divisors(n): A:=[seq(div[j]+1, j=1..tau(n))]: B:={}: for i from 1 to tau(n) do if isprime(A[i])=true then B:=B union {A[i]} else B:=B: fi: od: C:=convert(B, list): b[n]:=C: od: for n from 1 to 20 do b[n]:=b[n] od; # yields sequence in triangular form - Emeric Deutsch, Aug 03 2005
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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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EXTENSIONS
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STATUS
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approved
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