It is also a Stern prime , a Pell number , and a Markov number , appearing in infinitely many solutions to the Markov Diophantine equation involving odd-indexed Pell numbers .
It is also a Stern prime , a Pell number , the first Fibonacci prime , and a Markov number , appearing in infinitely many solutions to the Markov Diophantine equation involving odd-indexed Pell numbers .