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A341887 a(n) = A341886(n)/2; numbers k such that A307437(k) is even. 4
256, 512, 1024, 2816, 4096, 5632, 8192, 11264, 27136, 28928, 48896, 54272, 61184, 65536, 75008, 82688, 84992, 90112, 94464, 97792, 105216, 122368, 124160, 128000, 138240, 139520, 150016, 158720, 166656, 167168, 167936, 168704, 176128, 183808, 185856, 195584 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Indices of even terms in A307437; A341886 is the main entry.
Numbers k such that 2^k is a term: 8, 9, 10, 12, 13, 16, 18, 19, 20, 21, 22, 23, ... Are all sufficiently large powers of 2 terms? - Chai Wah Wu, Feb 24 2021
We don't know. From the comments in A341886, 2^k is a term if and only if t*2^(k+1)+1 is composite for t = 1, 2, 3. But we don't know if there are infinitely many Fermat primes. - Jianing Song, Feb 26 2021
All terms are divisible by 256. See my comment in A341886. - Jianing Song, Feb 27 2021
LINKS
EXAMPLE
psi(2048) = 512 is divisible by 2*256, and there is no odd m < 2048 such that 2*256 | psi(m), so 256 is a term.
psi(47104) = 5632 is divisible by 2*2816, and there is no m < 47104 such that 2*2816 | psi(m), so 2816 is a term.
PROG
(PARI) forstep(n=2, 10000, 2, if(A307437(n)%2==0, print1(n, ", "))) \\ see A307437 for its program
CROSSREFS
Sequence in context: A043336 A256822 A172422 * A031465 A045081 A294153
KEYWORD
nonn,hard
AUTHOR
Jianing Song, Feb 22 2021
EXTENSIONS
a(9)-a(20) from Michel Marcus, Feb 24 2021
a(21)-a(36) from Chai Wah Wu, Feb 24 2021
STATUS
approved

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Last modified July 13 18:54 EDT 2024. Contains 374285 sequences. (Running on oeis4.)