A300329 Number of solutions to +-1 +- 2 +- 3 +- ... +- n == n-1 (mod n).

2, 4, 2, 0, 6, 20, 18, 0, 56, 204, 186, 0, 630, 2340, 2182, 0, 7710, 29120, 27594, 0, 99858, 381300, 364722, 0, 1342176, 5162220, 4971008, 0, 18512790, 71582716, 69273666, 0, 260300986, 1010580540, 981706806, 0, 3714566310, 14467258260, 14096302710, 0

Offset

1,1

Links

Seiichi Manyama, Table of n, a(n) for n = 1..3333

Example

Solutions for n = 7:
--------------------------------------------------------------
1 +2 +3 +4 -5 -6 +7 =   6,         -1 +2 +3 -4 +5 -6 +7 =   6,
1 +2 +3 +4 -5 -6 -7 =  -8,         -1 +2 +3 -4 +5 -6 -7 =  -8,
1 +2 +3 -4 +5 +6 +7 =  20,         -1 +2 -3 +4 +5 +6 +7 =  20,
1 +2 +3 -4 +5 +6 -7 =   6,         -1 +2 -3 +4 +5 +6 -7 =   6,
1 +2 -3 -4 -5 -6 +7 =  -8,         -1 -2 +3 -4 -5 -6 +7 =  -8,
1 +2 -3 -4 -5 -6 -7 = -22,         -1 -2 +3 -4 -5 -6 -7 = -22,
1 -2 +3 -4 -5 +6 +7 =   6,         -1 -2 -3 +4 -5 +6 +7 =   6,
1 -2 +3 -4 -5 +6 -7 =  -8,         -1 -2 -3 +4 -5 +6 -7 =  -8,
1 -2 -3 +4 +5 -6 +7 =   6,
1 -2 -3 +4 +5 -6 -7 =  -8.

Prog

(PARI) a(n) = my (v=vector(n, k, k==1)); for (p=1, n, v = vector(n, k, v[1+(k-1+p)%n]+v[1+(k-1-p)%n])); v[1+(n-1)%n] \\ Rémy Sigrist, Mar 03 2018

Crossrefs

Cf. A300190, A300328.

Sequence in context: A335764 A202069 A364529 * A094239 A273240 A201316

Adjacent sequences: A300326 A300327 A300328 * A300330 A300331 A300332

Keyword

nonn

Author

Seiichi Manyama, Mar 03 2018

Status

approved