|
| |
|
|
A115167
|
|
Odd numbers k such that k-1 and k+1 have the same number of prime divisors with multiplicity.
|
|
2
|
|
|
|
5, 19, 29, 43, 51, 55, 67, 69, 77, 89, 115, 151, 171, 173, 187, 189, 197, 233, 237, 243, 245, 249, 267, 271, 283, 285, 291, 295, 307, 317, 329, 341, 343, 349, 355, 403, 405, 411, 427, 429, 435, 437, 461, 489, 491, 507, 569, 571, 593, 597, 603, 605, 653, 665
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
LINKS
|
Amiram Eldar, Table of n, a(n) for n = 1..10000
|
|
|
MATHEMATICA
|
s = {}; o1 = 0; Do[o2 = PrimeOmega[n]; If[o1 == o2, AppendTo[s, n-1]]; o1 = o2, {n, 2, 666, 2}]; s (* Amiram Eldar, Sep 23 2019 *)
|
|
|
PROG
|
(PARI) g(n) = forstep(x=3, n, 2, p1=bigomega(x-1); p2=bigomega(x+1); if(p1==p2, print1(x", ")))
(Python)
from sympy import primeomega
def aupto(limit):
prv, nxt, alst = 1, 2, []
for n in range(3, limit+1, 2):
if prv == nxt: alst.append(n)
prv, nxt = nxt, primeomega(n+3)
return alst
print(aupto(665)) # Michael S. Branicky, May 19 2021
|
|
|
CROSSREFS
|
Subsequence of A280382.
Sequence in context: A251623 A341079 A045456 * A115103 A241043 A045457
Adjacent sequences: A115164 A115165 A115166 * A115168 A115169 A115170
|
|
|
KEYWORD
|
easy,nonn
|
|
|
AUTHOR
|
Cino Hilliard, Mar 03 2006
|
|
|
STATUS
|
approved
|
| |
|
|
