|
|
A340008
|
|
a(n) is the image of n under the map: n -> n/2 if n is even, n-> n^2 - 1 if n is an odd prime, otherwise n -> n - 1.
|
|
8
|
|
|
0, 1, 8, 2, 24, 3, 48, 4, 8, 5, 120, 6, 168, 7, 14, 8, 288, 9, 360, 10, 20, 11, 528, 12, 24, 13, 26, 14, 840, 15, 960, 16, 32, 17, 34, 18, 1368, 19, 38, 20, 1680, 21, 1848, 22, 44, 23, 2208, 24, 48, 25, 50, 26, 2808, 27, 54, 28, 56, 29, 3480, 30, 3720, 31, 62, 32
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,3
|
|
COMMENTS
|
|
|
LINKS
|
|
|
MATHEMATICA
|
Array[Which[EvenQ@ #, #/2, PrimeQ@ #, #^2 - 1, True, # - 1] &, 64] (* Michael De Vlieger, Dec 28 2020 *)
|
|
PROG
|
(Python)
from sympy import isprime
for n in range(1, 1001):
if n%2 == 0: a = n/2
elif isprime(n) == 1: a = n*n - 1
else: a = n - 1
print(a)
(PARI) a(n) = if (n%2, if (isprime(n), n^2-1, n-1), n/2); \\ Michel Marcus, Dec 26 2020
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|