A270840 Numbers n such that n^3 + 1 is a 2-pseudoprime (or Sarrus number).

12, 36, 138, 270, 546, 4800, 7560, 12840, 14700, 358200, 678480, 16139970, 22934100, 55058580, 59553720, 74371320, 113068380, 116605860, 242699310, 997521210, 1592680320, 1652749200, 3190927740, 5088964800, 6974736756, 9214178820

Offset: 1

Author

Jeppe Stig Nielsen, Mar 23 2016

Keywords

• nonn

Comments

Since n^3 + 1 is clearly composite (n>1), this is n such that 2^(n^3) == 1 (mod n^3+1).

There is only one n such that n + 1 is a composite number up to 10^10: 14700. - Altug Alkan, Mar 27 2016

Crossrefs

Cf. A001567, A135590, A265653.

Programs

PARI

is(n)=Mod(2,n^3+1)^(n^3)==1

Formula

a(n) = A265653(n) - 1. - Altug Alkan, Mar 24 2016

Extensions

More terms from Altug Alkan, Mar 24 2016