|
| |
|
|
A069896
|
|
GCD of consecutive values of Chowla's function.
|
|
2
|
|
|
|
0, 0, 2, 2, 5, 5, 6, 3, 1, 7, 15, 15, 9, 1, 2, 14, 20, 20, 21, 1, 1, 13, 35, 5, 5, 3, 3, 27, 41, 41, 30, 2, 1, 1, 6, 54, 21, 1, 1, 49, 53, 53, 39, 1, 1, 25, 75, 1, 7, 2, 5, 45, 65, 1, 1, 1, 1, 31, 107, 107, 33, 1, 2, 2, 1, 77, 57, 1, 1, 73, 122, 122, 39, 3, 3, 9, 1, 89, 105, 3, 1, 43
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,3
|
|
|
LINKS
|
|
|
|
FORMULA
|
a(n) = gcd(sigma(n+1)-(n+1)-1, sigma(n)-n-1), for n > 1.
|
|
|
EXAMPLE
|
Chowla's function values from 92 to 96 are 75,34,49,24,155: successive values are relatively primes.
|
|
|
MATHEMATICA
|
m = 100; s = Array[If[# == 1, 0, DivisorSigma[1, #] - # - 1] &, {m}]; GCD[s[[1 ;; m - 1]], s[[2 ;; m]]] (* Amiram Eldar, Aug 28 2019 *)
|
|
|
CROSSREFS
|
|
|
|
KEYWORD
|
easy,nonn
|
|
|
AUTHOR
|
|
|
|
EXTENSIONS
|
|
|
|
STATUS
|
approved
|
| |
|
|
