A374823 Primes p such that p-1 is refactorable.

2, 3, 13, 19, 37, 41, 61, 73, 89, 97, 109, 137, 157, 181, 229, 233, 241, 277, 349, 373, 397, 449, 569, 601, 613, 641, 673, 709, 733, 809, 829, 853, 857, 877, 881, 883, 937, 997, 1049, 1069, 1097, 1117, 1153, 1193, 1201, 1213, 1237, 1249, 1361, 1409, 1433, 1549, 1621, 1657, 1669, 1693, 1789, 1801

Offset

1,1

Comments

Primes p such that p - 1 is divisible by A000005(p-1), the number of divisors of p - 1.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(4) = 19 is a term because 19 is prime and 18 is divisible by A000005(18) = 6.

Maple

filter:= p -> isprime(p) and (p-1) mod numtheory:-tau(p-1) = 0:
select(filter, [2, seq(i, i=3..10000, 2)]);

Crossrefs

Intersection of A000040 and A377121.

Includes A158018 and A158014 (except 17).

Cf. A000005, A033950.

Sequence in context: A194598 A080359 A193507 * A368396 A103087 A302485

Adjacent sequences: A374820 A374821 A374822 * A374824 A374825 A374826

Keyword

nonn

Author

Robert Israel, Dec 12 2024

Status

approved