1.5 KiB
id | title | challengeType | forumTopicId | dashedName |
---|---|---|---|---|
5900f4eb1000cf542c50fffd | Problem 382: Generating polygons | 5 | 302046 | problem-382-generating-polygons |
--description--
A polygon is a flat shape consisting of straight line segments that are joined to form a closed chain or circuit. A polygon consists of at least three sides and does not self-intersect.
A set S
of positive numbers is said to generate a polygon P
if:
- no two sides of
P
are the same length, - the length of every side of
P
is inS
, and S
contains no other value.
For example:
The set {3, 4, 5} generates a polygon with sides 3, 4, and 5 (a triangle).
The set {6, 9, 11, 24} generates a polygon with sides 6, 9, 11, and 24 (a quadrilateral).
The sets {1, 2, 3} and {2, 3, 4, 9} do not generate any polygon at all.
Consider the sequence s
, defined as follows:
s_1 = 1
,s_2 = 2
,s_3 = 3
s_n = s_{n - 1} + s_{n - 3}
forn > 3
.
Let U_n
be the set \\{s_1, s_2, \ldots, s_n\\}
. For example, U_{10} = \\{1, 2, 3, 4, 6, 9, 13, 19, 28, 41\\}
.
Let f(n)
be the number of subsets of U_n
which generate at least one polygon.
For example, f(5) = 7
, f(10) = 501
and f(25) = 18\\,635\\,853
.
Find the last 9 digits of f({10}^{18})
.
--hints--
generatingPolygons()
should return 697003956
.
assert.strictEqual(generatingPolygons(), 697003956);
--seed--
--seed-contents--
function generatingPolygons() {
return true;
}
generatingPolygons();
--solutions--
// solution required