A381256 Numbers k such that 5*k+1 divides 5^k+1.

0, 1, 625, 57057, 7748433, 30850281, 111494625, 393423745, 499088601, 519341361, 1051107705, 1329416385, 1616038425, 2215448001, 2433936225, 2852972265, 3399207273, 4344683849, 4961725281, 5454760185, 5485530369, 6578054145, 6678031745, 7701979761, 7807302825

Offset: 1

Author

René-Louis Clerc, Feb 18 2025

Keywords

• nonn

Comments

The numbers are called Curzon numbers by Tattersall (p. 85, exercise 43).

Examples

			5*625+1 = 3126 divides 5^625+1.
		

References

• James J. Tattersall, Elementary Number Theory in Nine Chapters, Second Edition, Cambridge University Press, 2005, p. 85.

Links

• Giovanni Resta, Curzon numbers, Numbers Aplenty.

Crossrefs

Cf. A224486, A222948, A230076, A381257, A381258.

Programs

PARI

isok(n) = my(m=5*n+1); Mod(5, m)^n==-1