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, 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.

Links

Table of n, a(n) for n=0..6.

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

Adjacent sequences: A111655 A111656 A111657 * A111659 A111660 A111661

Keyword

easy,nonn

Author

Stuart M. Ellerstein (ellerstein(AT)aol.com), Nov 17 2005

Status

approved