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Search: id:A111658
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| A111658 |
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Pronic residues. These are analogous to quadratic residues, but use the set of pronics 0 2 6 12 20 30... instead of the quadratics (squares) 0 1 4 9 16 25... The example shown above is mod 13. |
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+0
1
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OFFSET
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0,2
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COMMENT
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It is noted that when the modulus is not prime that a 0 may appear in the interior of the sequence. example for mod (15). 0 2 6 12 5 0 12 11.
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FORMULA
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Prn(i) -= r(i) mod (z) where Prn(i) is the i-th pronic, -= is the congruence sign, r(i) is the i-th residue and mod (z) is the modulus used.
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EXAMPLE
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r(5) = 7 mod (13).
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CROSSREFS
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Sequence in context: A014965 A074259 A113540 this_sequence A105692 A107647 A145102
Adjacent sequences: A111655 A111656 A111657 this_sequence A111659 A111660 A111661
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KEYWORD
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easy,nonn
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AUTHOR
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Stuart M. Ellerstein (ellerstein(AT)aol.com), Nov 17 2005
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