OFFSET
1,1
COMMENTS
Conjecture: a(n) ~ 7.75*n.
LINKS
Christian N. K. Anderson, Table of n, a(n) for n = 1..10000
EXAMPLE
217 = 7*31, but 127 is prime. 302 = 2*151, but 23 is prime.
MATHEMATICA
Select[Range[500], ! PrimeQ[#] && PrimeQ[FromDigits[Sort[IntegerDigits[#]]]] &] (* T. D. Noe, Apr 05 2013 *)
PROG
(R) j=1; y=c(); library(gmp)
while(length(y)<1000) {
if(isprime((j=j+1))==0) {
x=sort(as.numeric(strsplit(as.character(j), spl="")[[1]]))
if(isprime(paste(x[x>0], collapse=""))>0) y=c(y, j) #drop leading zeros
}
}
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Christian N. K. Anderson and Kevin L. Schwartz, Apr 05 2013
STATUS
approved