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A364549
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Odd numbers k that divide A005941(k).
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4
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1, 3, 5, 97, 345, 549, 1093, 64621, 671515, 3280317, 8957089
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OFFSET
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1,2
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COMMENTS
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Odd numbers k such that k divides 1+A156552(k).
The first ten terms factored:
1 (unity)
3 (prime)
5 (prime)
97 (prime)
345 = 3*5*23
549 = 3^2 * 61
1093 (prime)
64621 (prime)
671515 = 5*13*10331
3280317 = 3*79*13841.
Primes p present are those that occur as factors of 1 + 2^(A000720(p)-1).
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LINKS
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PROG
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(PARI)
A005941(n) = { my(f=factor(n), p, p2=1, res=0); for(i=1, #f~, p = 1 << (primepi(f[i, 1])-1); res += (p * p2 * (2^(f[i, 2])-1)); p2 <<= f[i, 2]); (1+res) }; \\ (After David A. Corneth's program for A156552)
isA364549(n) = ((n%2)&&!(A005941(n)%n));
(Python)
from itertools import count, islice
from sympy import primepi, factorint
def A364549_gen(startvalue=1): # generator of terms >= startvalue
for n in count(max(startvalue+(startvalue&1^1), 1), 2):
if not (sum(pow(2, i+int(primepi(p))-1, n) for i, p in enumerate(factorint(n, multiple=True)))+1) % n:
yield n
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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