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A111658
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.
0
0, 2, 6, 12, 7, 4, 3
OFFSET
0,2
COMMENTS
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.
FORMULA
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.
EXAMPLE
r(5) = 7 mod (13).
CROSSREFS
Sequence in context: A074259 A338376 A113540 * A341664 A105692 A107647
KEYWORD
easy,nonn
AUTHOR
Stuart M. Ellerstein (ellerstein(AT)aol.com), Nov 17 2005
STATUS
approved