A353221 Squarefree base-2 Fermat pseudoprimes divisible by a Wieferich prime.

3581761, 5173169, 5968873, 23872213, 36974341, 53711113, 107023281, 427294141, 490950461, 526359289, 546649741, 550230409, 753532781, 803264281, 836683849, 1115578101, 1168492417, 1193557093, 1540454761, 1632785701, 2129304997, 2295209281, 2677147201

Offset: 1

Author

Felix Fröhlich, May 01 2022

Keywords

• nonn

Comments

Subsequence of A001567.

The least term that is divisible by both 1093 and 3511 is a(799) = 7015325908501 = 937 * 1093 * 1951 * 3511. - Amiram Eldar, May 05 2022

Examples

			3581761 = 29 * 113 * 1093, so it is a base-2 pseudoprime divisible by the Wieferich prime 1093 and is squarefree.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000
• PrimeGrid, Subproject status.

Crossrefs

Cf. A001220, A001567, A158358, A219346, A247830, A247831, A295740.

Programs

PARI

/* The following program is valid up to the current search bound for Wieferich primes, about 10^19 as of May 03 2022 (cf. PrimeGrid); the program may miss terms above that bound if there is another Wieferich prime */
forcomposite(c=1, , if(Mod(2, c)^(c-1)==1, if(Mod(c, 1093)==0 || Mod(c, 3511)==0, if(issquarefree(c), print1(c, ", ")))))