|
| |
|
|
A165801
|
|
f(n), f(f(n)), ... are all prime, where f(n) = (n-1)/2. Stop when f(...f(n)...) is less than 4.
|
|
3
| | |
|
|
|
OFFSET
| 1,2
|
|
|
COMMENTS
| There are no more terms since 95 is composite.
|
|
|
EXAMPLE
| (95-1)/2=47(prime); (47-1)/2=23(prime); (23-1)/2=11(prime); (11-1)/2=5(prime); (5-1)/2=2(prime); no composite numbers smaller then 2 exists,end. (47-1)/2=23(prime);(23-1)/2=11(prime); (11-1)/2=5(prime); (5-1)/2=2;no composite numbers smaller then 2 exists,end.
|
|
|
MATHEMATICA
| f[n_]:=Module[{k=n}, While[k>3, k=(k-1)/2; If[ !PrimeQ[k], Break[]]]; PrimeQ[k]]; lst={}; Do[If[f[n], AppendTo[lst, n]], {n, 5!}]; lst
|
|
|
CROSSREFS
| Sequence in context: A055771 A052955 A177485 * A022480 A024791 A178240
Adjacent sequences: A165798 A165799 A165800 * A165802 A165803 A165804
|
|
|
KEYWORD
| nonn,easy,fini,full
|
|
|
AUTHOR
| Vladimir Orlovsky (4vladimir(AT)gmail.com), Sep 28 2009
|
|
|
EXTENSIONS
| Corrected and edited by Charles R Greathouse IV (charles.greathouse(AT)case.edu), Oct 05 2009
|
| |
|
|
