OFFSET
0,2
COMMENTS
LINKS
Robert Israel, Table of n, a(n) for n = 0..10000
EXAMPLE
a(22) = 21: the concatenation of 21 and 21 + 22 = 43 is 2143 and this is a prime.
MAPLE
tcat:= (a, b) -> a*10^(1+ilog10(b))+b:
f:= proc(n) local k;
for k from 1 + (n mod 2) by 2 do
if isprime(tcat(k, k+n)) then return k fi
od;
end proc:
map(f, [$0..100]); # Robert Israel, Sep 05 2024
CROSSREFS
KEYWORD
AUTHOR
Patrick De Geest, May 15 1998
EXTENSIONS
Edited by Robert Israel, Sep 05 2024
STATUS
approved