A128682 Numbers k such that k^3 divides 9^(k^2) + 1.

1, 5, 505, 5905, 596405, 1971005, 199071505, 515151005, 581457505, 618181105, 2327756905, 11855474405, 19555113485, 31361954905, 101901244565, 235103447405, 305354088005, 395331063745, 600905819065, 608393336905, 686701313405, 730071885005

Offset: 1

Author

Alexander Adamchuk, Mar 31 2007

Keywords

• nonn

Comments

5 divides a(n) for n > 1.

Crossrefs

Cf. A127263, A128677, A128678, A128679, A128680, A128681, A128683, A128684, A128685.

Programs

Mathematica

Select[Range[5*10^6], Mod[ 9^(#^2)+1, #^3]==0 &] (* G. C. Greubel, Jan 18 2018 *)

Extensions

a(5)-a(6) from J. Mulder (jasper.mulder(AT)planet.nl), Jan 26 2010

Terms a(7) onward from Max Alekseyev, May 14 2010