OFFSET
1,7
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
See the example in A069842.
MAPLE
f:= proc(n) local k;
if member(n mod 10, {0, 2, 4, 5, 6, 8}) then if isprime(10*n+9) then return 1 else return 0 fi fi;
nops(select(isprime, {seq(9*10^k + 10^(k+1)*floor(n/10^k) + (n mod 10^k), k=0..ilog10(n)+1)}));
end proc:
map(f, [$1..200]); # Robert Israel, Oct 09 2020
MATHEMATICA
Table[ Count[ PrimeQ[ Union[ FromDigits /@ Table[ Insert[ IntegerDigits[n], 9, j], {j, 1, Floor[ Log[10, n] + 2]}]]], True], {n, 1, 105}]
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Apr 16 2002
EXTENSIONS
More terms from Vladeta Jovovic, Apr 17 2002
Edited by Robert G. Wilson v, Apr 18 2002
STATUS
approved