login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

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

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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