A180784 Number of distinct solutions of sum{i=1..2}(x(2i-1)*x(2i)) = 1 (mod n), with x() only in 1..n-1.

0, 0, 1, 4, 9, 19, 31, 42, 75, 91, 136, 160, 232, 254, 364, 388, 542, 525, 767, 754, 1015, 993, 1389, 1256, 1795, 1641, 2169, 2080, 2838, 2344, 3484, 3144, 3971, 3676, 4980, 4152, 5989, 5135, 6564, 6008, 8195, 6392, 9476, 8064, 9912, 9114, 12426, 9808, 14032

Offset

1,4

Comments

Column 2 of A180793

Links

R. H. Hardin, Table of n, a(n) for n=1..999

Example

Solutions for sum of products of 2 1..5 pairs = 1 (mod 6) are
(1*1 + 2*3) (1*1 + 3*4) (1*2 + 1*5) (1*3 + 1*4) (1*3 + 2*2) (1*3 + 2*5)
(1*3 + 4*4) (1*4 + 3*3) (1*4 + 3*5) (1*5 + 2*4) (1*5 + 4*5) (2*2 + 3*3)
(2*2 + 3*5) (2*3 + 5*5) (2*5 + 3*3) (2*5 + 3*5) (3*3 + 4*4) (3*4 + 5*5)
(3*5 + 4*4)

Crossrefs

Sequence in context: A327753 A100448 A059820 * A015618 A086733 A254100

Adjacent sequences: A180781 A180782 A180783 * A180785 A180786 A180787

Keyword

nonn

Author

R. H. Hardin, Sep 20 2010

Status

approved