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A349309 Numbers k such that A254926(k) = A254926(k+1). 2
7, 26, 124, 342, 1330, 2196, 12166, 24388, 29790, 79506, 103822, 148876, 205378, 226980, 300762, 357910, 493038, 571786, 1030300, 1092726, 1225042, 2248090, 2685618, 3307948, 3442950, 3869892, 4657462, 5177716, 5735338, 6967870, 7645372, 9393930, 11089566, 11697082 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
7 is a term since A254926(7) = A254926(8) = 7.
MATHEMATICA
f[p_, e_] := If[e < 3, p^e, p^e - p^(e - 3)]; s[n_] := Times @@ f @@@ FactorInteger[n]; Select[Range[10^6], s[#] == s[# + 1] &]
PROG
(Python)
from math import prod
from itertools import count, islice
from sympy import factorint
def A349309_gen(startvalue=1): # generator of terms >= startvalue
a = prod(p**e - (p**(e-3) if e >= 3 else 0) for p, e in factorint(max(startvalue, 1)).items())
for k in count(max(startvalue, 1)):
b = prod(p**e - (p**(e-3) if e >= 3 else 0) for p, e in factorint(k+1).items())
if a == b:
yield k
a = b
A349309_list = list(islice(A349309_gen(), 10)) # Chai Wah Wu, Jan 24 2022
CROSSREFS
Cf. A254926.
Sequence in context: A240261 A232605 A350473 * A262110 A319425 A026683
KEYWORD
nonn
AUTHOR
Amiram Eldar, Nov 14 2021
STATUS
approved

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Last modified June 19 18:58 EDT 2024. Contains 373507 sequences. (Running on oeis4.)