A250290 Numbers k such that Euler(k) (A122045(k)) is a semiprime.

8, 10, 14, 26, 30, 58, 78

Offset: 1

Author

Eric Chen, Dec 24 2014

Keywords

• nonn
• more

Comments

No more terms <= 200.

k=7634 is a term, but it is not known to be the next term after 78. - Jeppe Stig Nielsen, May 12 2023

Examples

			a(2) = 10 so Euler(10) = 50521 = 19 * 2659 is a semiprime.
		

Links

• Hisanori Mishima, Euler numbers (n = 0 to 78).
• Hisanori Mishima, Euler numbers (n = 80 to 106).
• Prime Pages, -E(7634)/1559.
• Sam Wagstaff, Factorization of Bernoulli and Euler numbers.

Crossrefs

Cf. A103234, A122045.

Programs

PARI

is(k) = k%2==0 && bigomega(eulerfrac(k))==2 \\ slow, from Jeppe Stig Nielsen, May 12 2023