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

1,1

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

Links

Table of n, a(n) for n=1..24.

Example

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

Mathematica

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

Crossrefs

Cf. A002522, A005574, A005935, A135590.

Sequence in context: A304369 A074266 A208089 * A275154 A066890 A242296

Adjacent sequences: A333313 A333314 A333315 * A333317 A333318 A333319

Keyword

nonn,more

Author

Amiram Eldar, Mar 14 2020

Extensions

a(24) from Giovanni Resta, Mar 15 2020

Status

approved