OFFSET
1,1
COMMENTS
Except for the number 22, the sequence A176597 (double primes: concatenation of the n-th prime with itself) is a subsequence of this sequence.
EXAMPLE
a(8) = 8051 = 83*97 => 8051 and 83 start with 8.
MAPLE
with(numtheory): for n from 1 to 60 do: l1:=length(n):i:=0:for m from 2 to 32*10^6 while(i=0) do: x:=factorset(m):y:=x[1]: l2:=length(m):x1:=floor(m/(10^(l2-l1))): l3:=length(y):x2:=floor(y/(10^(l3-l1))):if x1=n and x2=n and l2>=l1 and l3 >=l1 and type(m, prime)=false then i:=1: printf ( "%d %d \n", n, m):else fi :od:od:
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Michel Lagneau, Oct 18 2011
STATUS
approved