A293626 Numbers of the form (2^(2p) + 1)/5, where p is a prime > 5.

3277, 838861, 13421773, 3435973837, 54975581389, 14073748835533, 57646075230342349, 922337203685477581, 3777893186295716170957, 967140655691703339764941, 15474250491067253436239053, 3961408125713216879677197517, 16225927682921336339157801028813

Offset: 1

Author

Amiram Eldar, Oct 13 2017

Keywords

• nonn

Comments

Rotkiewicz proved that all the terms in this sequence are Fermat pseudoprimes to base 2 (A001567).

Examples

			3277 = (2^(2*7) + 1)/5 is the first term, corresponding to the prime p = 7.
		

Links

• Andrzej Rotkiewicz, Sur les formules donnant des nombres pseudopremiers, Colloquium Mathematicae, Vol. 12, No. 1 (1964), pp. 69-72.

Crossrefs

Cf. A001567, A210454.

Programs

Mathematica

p = Select[Range[7,60], PrimeQ]; (2^(2p) + 1)/5