|
| |
|
|
A077783
|
|
Palindromic wing primes (a.k.a. near-repdigit palindromes) of the form (10^a(n)-1)/9+4*10^[ a(n)/2 ].
|
|
1
| | |
|
|
|
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
| Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)
Makoto Kamada, Prime numbers of the form 11...11511...11
Index entries for primes involving repunits.
|
|
|
FORMULA
| a(n) = 2*A107125(n)+1.
|
|
|
EXAMPLE
| a(n)=15 -> (10^15-1)/9+4*10^7 = 111111151111111.
|
|
|
MATHEMATICA
| Do[ If[ PrimeQ[(10^n + 36*10^Floor[n/2] - 1)/9], Print[n]], {n, 3, 26400, 2}] (from Robert G. Wilson v (rgwv(at)rgwv.com), Dec 16 2005)
|
|
|
CROSSREFS
| Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.
Sequence in context: A185369 A024339 A034954 * A047019 A099251 A171790
Adjacent sequences: A077780 A077781 A077782 * A077784 A077785 A077786
|
|
|
KEYWORD
| more,nonn,base
|
|
|
AUTHOR
| Patrick De Geest (pdg(AT)worldofnumbers.com), Nov 16 2002.
|
| |
|
|
