|
Search: id:A065725
|
|
|
| A065725 |
|
Primes p such that the decimal expansion of its base 7 conversion is also prime. |
|
+0
1
|
|
| 2, 3, 5, 17, 29, 31, 43, 59, 71, 127, 157, 197, 211, 227, 239, 241, 337, 353, 367, 379, 409, 463, 491, 563, 577, 619, 647, 743, 757, 773, 787, 857, 911, 953, 967, 1093, 1123, 1163, 1193, 1249, 1303, 1373, 1429, 1459, 1471, 1499, 1583, 1597, 1613, 1627, 1669
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
In general rebase notation (Marc LeBrun): p(n) = (7) [p] (10).
|
|
LINKS
|
Harry J. Smith, Table of n, a(n) for n=1,...,1000
|
|
EXAMPLE
|
E.g. 787{10} = 2203{7} is prime but also 2203{10}.
|
|
MATHEMATICA
|
Select[ Range[2500], PrimeQ[ # ] && PrimeQ[ FromDigits[ IntegerDigits[ #, 7]]] & ]
|
|
PROGRAM
|
(PARI) baseE(x, b)= { local(d, e=0, f=1); while (x>0, d=x-b*(x\b); x\=b; e+=d*f; f*=10); return(e) } { n=0; for (m=1, 10^9, p=prime(m); b=baseE(p, 7); if (isprime(b), write("b065725.txt", n++, " ", p); if (n==1000, return)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 27 2009]
|
|
CROSSREFS
|
Cf. A065720 up to A065727, A065361.
Sequence in context: A055472 A077499 A127061 this_sequence A057468 A127062 A029972
Adjacent sequences: A065722 A065723 A065724 this_sequence A065726 A065727 A065728
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
Patrick De Geest (pdg(AT)worldofnumbers.com), Nov 15 2001.
|
|
|
Search completed in 0.002 seconds
|
