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 A067526 Numbers n such that n - 2^k is a prime or 1 for all k satisfying 0 < k, 2^k < n. 6
 3, 4, 5, 7, 9, 15, 21, 45, 75, 105 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Is the sequence finite? LINKS EXAMPLE 45 belongs to this sequence as 45-2, 45-4, 45-8, 45-16, 45-32, 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 (n-2^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

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Last modified May 23 07:00 EDT 2019. Contains 323508 sequences. (Running on oeis4.)