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Odd numbers k that divide 25^k - 1.
1

%I #19 Jul 02 2021 01:57:27

%S 1,3,9,21,27,63,81,93,147,171,189,243,279,441,513,567,609,651,729,837,

%T 903,1029,1197,1323,1539,1701,1827,1953,2187,2511,2667,2709,2883,2943,

%U 3087,3249,3591,3969,4263,4401,4557,4617,5103,5301,5481,5859,6321

%N Odd numbers k that divide 25^k - 1.

%C Also, numbers k such that k divides s(k), where s(1)=1, s(j) = s(j-1) + j*25^(j-1).

%C Equivalently, numbers k that divide ((24*k - 1)*25^k + 1) / 24^2 (cf. A014943).

%H Robert Israel, <a href="/A014962/b014962.txt">Table of n, a(n) for n = 1..10000</a>

%p select(t -> 25 &^ t - 1 mod t = 0, [seq(i,i=1..10^4,2)]); # _Robert Israel_, Oct 04 2020

%Y Cf. A014943, A014945, A014946, A014949, A014950, A014951, A014956, A014957, A128358, A128360, A014959, A014960.

%K nonn

%O 1,2

%A _Olivier GĂ©rard_

%E Edited by _Max Alekseyev_, Nov 16 2019