A352970 Carmichael numbers ending in 9.

1729, 294409, 1033669, 1082809, 1773289, 5444489, 7995169, 8719309, 17098369, 19384289, 23382529, 26921089, 37964809, 43620409, 45890209, 50201089, 69331969, 84311569, 105309289, 114910489, 146843929, 168659569, 172947529, 180115489, 188516329, 194120389, 214852609, 228842209, 230996949, 246446929, 271481329

Offset: 1

Author

Omar E. Pol, Apr 12 2022

Keywords

• nonn
• base

Comments

The first term is the Hardy-Ramanujan number.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..109 from Chai Wah Wu)
• Index entries for sequences related to Carmichael numbers.

Crossrefs

Intersection of A002997 and A017377.

Subsequence of A053181.

Cf. A001235, A354609, A355305, A355307, A355309.

Programs

Mathematica

Select[10*Range[0, 3*10^7] + 9, CompositeQ[#] && Divisible[# - 1, CarmichaelLambda[#]] &] (* Amiram Eldar, May 28 2022 *)

Python

from itertools import islice
from sympy import factorint, nextprime
def A352970_gen(): # generator of terms
    p, q = 3, 5
    while True:
        for n in range(p+11-((p+2) % 10),q,10):
            f = factorint(n)
            if max(f.values()) == 1 and not any((n-1) % (p-1) for p in f):
                yield n
        p, q = q, nextprime(q)
A352970_list = list(islice(A352970_gen(),5)) # Chai Wah Wu, May 11 2022