OFFSET
1,1
COMMENTS
In general rebase notation (Marc LeBrun): p9 = (9) [p] (10).
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
EXAMPLE
E.g., 997_10 = 1327_9 is prime, and so is 1327_10.
MATHEMATICA
Select[ Range[2500], PrimeQ[ # ] && PrimeQ[ FromDigits[ IntegerDigits[ #, 9]]] & ]
NestList[NestWhile[NextPrime, #, ! PrimeQ[FromDigits[IntegerDigits[#2, 9]]] &, 2] &, 2, 48] (* Jan Mangaldan, Jul 01 2020 *)
Select[Prime[Range[400]], PrimeQ[FromDigits[IntegerDigits[#, 9], 10]]&] (* Harvey P. Dale, Sep 19 2021 *)
PROG
(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, 9); if (isprime(b), write("b065727.txt", n++, " ", p); if (n==1000, return)) ) } \\ Harry J. Smith, Oct 28 2009
(PARI) isok(p) = isprime(p) && isprime(fromdigits(digits(p, 9))); \\ Michel Marcus, Jul 02 2020
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Nov 15 2001
STATUS
approved