A280005 Least prime p such that p^n + 1 is the product of n distinct primes.

2, 3, 13, 43, 73, 47, 457, 1697, 109, 8161, 10429, 13183, 30089, 66569, 5281

Offset

1,1

Comments

Corresponding values of p^n + 1 are 3, 10, 2198, 3418802, 2073071594, 10779215330, 4163067000501310394, ...

a(16) <= 206874667. - Daniel Suteu, Dec 09 2022

Links

Table of n, a(n) for n=1..15.

Example

a(2) = 3; 3^2 + 1 = 2 * 5.
a(3) = 13; 13^3 + 1 = 2 * 7 * 157.
a(4) = 43; 43^4 + 1 = 2 * 17 * 193 * 521.

Prog

(PARI) a(n) = my(p=2); while (!issquarefree(p^n+1) || omega(p^n+1) != n, p = nextprime(p+1)); p;

Crossrefs

Cf. A000961, A005117, A362957.

Sequence in context: A122719 A106866 A278139 * A235626 A164133 A226938

Adjacent sequences: A280002 A280003 A280004 * A280006 A280007 A280008

Keyword

nonn,hard,more

Author

Altug Alkan, Feb 24 2017

Status

approved