|
Search: id:A108817
|
|
|
| A108817 |
|
Primes of the form n*10^x + n - 1, where 0 < n < 9, x = 0,1,2,3... |
|
+0
1
|
|
| 3, 5, 7, 11, 13, 43, 4003, 40000003, 40000000003, 40000000000000000000000000000000000000003
(list; graph; listen)
|
|
|
OFFSET
|
0,1
|
|
|
COMMENT
|
The next 2 terms for x <= 1000 are 4*10^419+3 and 4*10^449+3 both Pari proved primes. Except for the first 5 terms, the outer digits of these numbers are 4 and 3. This follows from the fact that all other combinations produce multiples of 2,3 or 5.
|
|
EXAMPLE
|
n=4,x=3. a(x,n) = 4*10^3+4-1 = 4003 prime.
|
|
PROGRAM
|
(PARI) n10nm1(n) = { local(x, y, k); for(x=0, n, for(k=1, 8, y=10^x*k+k-1; if(isprime(y), print1(y", ")) ) ) }
|
|
CROSSREFS
|
Adjacent sequences: A108814 A108815 A108816 this_sequence A108818 A108819 A108820
Sequence in context: A088878 A038979 A093988 this_sequence A123677 A133954 A087325
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Cino Hilliard (hillcino368(AT)gmail.com), Jul 11 2005
|
|
|
Search completed in 0.002 seconds
|
