|
Search: id:A077778
|
|
|
| A077778 |
|
Palindromic wing primes (a.k.a. near-repdigit palindromes) of the form (10^a(n)-1)-7*10^[ a(n)/2 ]. |
|
+0
2
|
|
| 3, 17, 19, 705, 1061, 1395, 2631, 3837, 5749, 11753, 13537
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
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, Factorizations of 99...99299...99
|
|
FORMULA
|
a(n) = 2*A115073(n)+1.
|
|
EXAMPLE
|
a(n)=17 -> (10^17-1)-7*10^8 = 99999999299999999.
|
|
MATHEMATICA
|
Do[ If[ PrimeQ[10^n - 7*10^Floor[n/2] - 1], Print[n]], {n, 3, 14600, 2}] (from Robert G. Wilson v (rgwv(at)rgwv.com), Dec 16 2005)
|
|
CROSSREFS
|
Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A114633-A114647.
Sequence in context: A032923 A018750 A147845 this_sequence A022127 A093024 A109990
Adjacent sequences: A077775 A077776 A077777 this_sequence A077779 A077780 A077781
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
Patrick De Geest (pdg(AT)worldofnumbers.com), Nov 16 2002.
|
|
|
Search completed in 0.002 seconds
|
