A333316 Numbers k such that k^2 + 1 is a Fermat pseudoprime to base 3.

216, 660, 1484, 1560, 8208, 52164, 544320, 592956, 649800, 4321800, 5103210, 6182220, 10621380, 21415680, 24471720, 135307008, 359624088, 535019100, 1071782250, 1113233520, 1227427740, 1527496740, 9462748008, 143935711920

Offset: 1

Author

Amiram Eldar, Mar 14 2020

Keywords

• nonn
• more

Comments

a(24) > 7*10^10.

The corresponding pseudoprimes a(n)^2 + 1 are 46657, 435601, 2202257, 2433601, 67371265, ...

a(25) > 7.5*10^11. - Giovanni Resta, Mar 15 2020

Examples

			216 is a term since 216^2 + 1 = 46657 is a Fermat pseudoprime to base 3.
		

Crossrefs

Cf. A002522, A005574, A005935, A135590.

Programs

Mathematica

Select[Range[10^3], CompositeQ[#^2 + 1] && PowerMod[3, #^2, #^2 + 1] == 1 &]

Extensions

a(24) from Giovanni Resta, Mar 15 2020