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

1,3

Comments

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

References

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

Links

Table of n, a(n) for n=1..25.

Giovanni Resta, Curzon numbers, Numbers Aplenty.

Example

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

Prog

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

Crossrefs

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

Sequence in context: A017224 A106321 A017332 * A167039 A265932 A017452

Adjacent sequences: A381253 A381254 A381255 * A381257 A381258 A381259

Keyword

nonn

Author

René-Louis Clerc, Feb 18 2025

Status

approved