

A067526


Numbers n such that n  2^k is a prime or 1 for all k satisfying 0 < k, 2^k < n.


6




OFFSET

1,1


COMMENTS

Is the sequence finite?


LINKS

Table of n, a(n) for n=1..10.


EXAMPLE

45 belongs to this sequence as 452, 454, 458, 4516, 4532, i.e. 43, 41, 37, 29 and 13 are all primes.


MATHEMATICA

f[n_] := Block[{k = 1}, While[2^k < n, k++ ]; k; k]; Do[ a = Table[n  2^k, {k, 1, f[n]} ]; If[ a[[ 1]] == 1, a = Drop[a, 1]]; If[ Union[ PrimeQ[a]] == {True}, Print[n]], {n, 5, 10^7, 2} ]


CROSSREFS

Cf. A039669 (n2^k is prime).
Sequence in context: A082922 A036971 A000702 * A101760 A165713 A105148
Adjacent sequences: A067523 A067524 A067525 * A067527 A067528 A067529


KEYWORD

nonn,hard,more


AUTHOR

Amarnath Murthy, Feb 17 2002


EXTENSIONS

Edited by Robert G. Wilson v, Feb 18 2002


STATUS

approved



