A045599 Numbers k that divide 10^k + 5^k.

1, 3, 5, 9, 15, 25, 27, 45, 55, 75, 81, 125, 135, 165, 171, 225, 243, 275, 375, 405, 495, 513, 605, 625, 675, 729, 825, 855, 1125, 1215, 1375, 1485, 1539, 1815, 1875, 2025, 2187, 2475, 2565, 3025, 3125, 3249, 3375, 3645, 4125, 4275, 4455, 4617, 4965, 5445

Offset

1,2

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[5500], Mod[PowerMod[10, #, #] +PowerMod[5, #, #], #]==0 &] (* G. C. Greubel, Dec 12 2022 *)

Prog

(Magma) [n: n in [1..5500] | (Modexp(10, n, n) + Modexp(5, n, n)) mod n eq 0 ]; // G. C. Greubel, Dec 12 2022
(SageMath) [n for n in (1..5500) if (power_mod(10, n, n)+power_mod(5, n, n))%n==0 ] # G. C. Greubel, Dec 12 2022
(PARI) is(n)=(Mod(10, n)^n+Mod(5, n)^n==0);
for(n=1, 5500, if(is(n), print1(n, ", "))); \\ Joerg Arndt, Dec 13 2022

Crossrefs

Cf. A000351, A011557.

Sequence in context: A178961 A147509 A057259 * A045604 A057251 A015965

Adjacent sequences: A045596 A045597 A045598 * A045600 A045601 A045602

Keyword

nonn

Author

David W. Wilson

Status

approved