

A067528


Numbers n such that n  4^k is a prime or 1 for all k > 0 and n > 4^k.


5



5, 6, 7, 9, 11, 15, 17, 21, 23, 27, 33, 35, 45, 47, 57, 63, 75, 77, 83, 87, 105, 117, 143, 153, 167, 195, 215, 227, 243, 245, 255, 287, 297, 413, 437, 447, 483, 495, 507, 525, 573, 635, 657, 677, 755, 825, 1113, 1133, 1295, 1487, 1515, 1547, 1617, 1623, 2015
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OFFSET

1,1


COMMENTS

Is the sequence finite?
The last term appears to be 5833497.  T. D. Noe, Nov 23 2004
A less strict version of A039669, n  2^k is prime for 0 < k < log_2 k. If a number is in that sequence, then obviously it is also in this sequence. As of this writing, 105 is believed to be the last term of that sequence.  Alonso del Arte, May 24 2017


LINKS



EXAMPLE

167 is a term as 167  4 = 163, 167  16 = 151, 167  64 = 103 are primes.


MAPLE

filter:= proc(n) local k, t;
for k from 1 do
if 4^k >= n1 then return true
elif not isprime(n4^k) then return false
fi
od
end proc:


MATHEMATICA

A067528 = {}; Do[k = 1; While[p = n  4^k; p > 0 && (p == 1  PrimeQ[p]), k++]; If[p <= 0, AppendTo[A067528, n]], {n, 5, 10^7}]; A067528 (* T. D. Noe *)


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



