A322629 For a nonnegative number m with decimal digits (d_1, ..., d_k), let s(m) be the area of the convex hull of the set of points { (i, d_i), i = 1..k }; a(n) = 2 * s(n).
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 3, 2, 1, 0, 1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 7, 6, 5, 4, 3, 2, 1, 0, 1, 2, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 15, 14, 13
Offset: 100
Examples
For n = 1212:
- the corresponding convex hull is as follows:
(2,2) +-----+ (4,2)
/ /
/ /
(1,1) +-----+ (3,1)
- it has area 2, hence a(1212) = 4.
Links
- Rémy Sigrist, Table of n, a(n) for n = 100..10000
- Rémy Sigrist, PARI program for A322629
Programs
-
PARI
\\ See Links section.
Comments