|
| |
|
|
A077788
|
|
Numbers k such that 7*(10^k - 1)/9 - 10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime).
|
|
2
|
|
|
|
9, 11, 17, 23, 2489, 3371, 4019, 29315, 30237, 40665, 101661, 150125
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
Prime versus probable prime status and proofs are given in the author's table.
|
|
|
REFERENCES
|
C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
|
|
|
LINKS
|
|
|
|
FORMULA
|
|
|
|
EXAMPLE
|
11 is a term because 7*(10^11 - 1)/9 - 10^5 = 77777677777.
|
|
|
MATHEMATICA
|
Do[ If[ PrimeQ[(7*10^n - 9*10^Floor[n/2] - 7)/9], Print[n]], {n, 3, 30300, 2}] (* Robert G. Wilson v, Dec 16 2005 *)
|
|
|
CROSSREFS
|
|
|
|
KEYWORD
|
more,nonn,base
|
|
|
AUTHOR
|
|
|
|
EXTENSIONS
|
|
|
|
STATUS
|
approved
|
| |
|
|
