|
| |
|
|
A077789
|
|
Palindromic wing primes (a.k.a. near-repdigit palindromes) of the form (10^a(n)-1)/9+6*10^[ a(n)/2 ].
|
|
2
|
| |
|
|
|
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
|
Table of n, a(n) for n=1..4.
Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)
Makoto Kamada, Prime numbers of the form 11...11711...11
Index entries for primes involving repunits.
|
|
|
FORMULA
|
a(n) = 2*A107127(n)+1.
|
|
|
EXAMPLE
|
a(n)=7 -> (10^7-1)/9+6*10^3 = 1117111.
|
|
|
MATHEMATICA
|
Do[ If[ PrimeQ[(10^n + 54*10^Floor[n/2] - 1)/9], Print[n]], {n, 3, 6000, 2}] (from Robert G. Wilson v, Dec 16 2005)
|
|
|
CROSSREFS
|
Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
Sequence in context: A139783 A103102 A139910 * A186655 A124291 A067275
Adjacent sequences: A077786 A077787 A077788 * A077790 A077791 A077792
|
|
|
KEYWORD
|
more,nonn,base
|
|
|
AUTHOR
|
Patrick De Geest, Nov 16 2002.
|
|
|
STATUS
|
approved
|
| |
|
|
