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 A057493 Numbers n such that n | 11^n + 10^n. 2

%I #16 Feb 23 2017 21:35:15

%S 1,3,7,9,21,27,49,63,81,111,147,171,189,203,243,333,343,441,513,567,

%T 609,729,777,999,1029,1143,1197,1323,1421,1539,1701,1791,1827,2187,

%U 2331,2401,2943,2997,3087,3249,3429,3591,3969,4107,4263,4617,5103,5373

%N Numbers n such that n | 11^n + 10^n.

%C From _Robert Israel_, Feb 23 2017: (Start)

%C Contains A003594.

%C Every term other than 1 is divisible by 3 or 7.

%C If m and n are in the sequence, then so is m*n. (End)

%H Robert Israel, <a href="/A057493/b057493.txt">Table of n, a(n) for n = 1..5305</a> (first 580 terms from Vincenzo Librandi)

%p select(t -> (10 &^ t + 11 &^ t mod t = 0), [seq(i,i=1..10000,2)]); # _Robert Israel_, Feb 23 2017

%t Select[ Range[ 10000 ], Mod[ PowerMod[ 11, #, # ] + PowerMod[ 10, #, # ], # ] == 0 & ]

%o (PARI) is(n)=Mod(11,n)^n+Mod(10,n)^n==0 \\ _Charles R Greathouse IV_, Feb 23 2017

%Y Cf. A003594.

%K nonn

%O 1,2

%A _Robert G. Wilson v_, Sep 20 2000

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Last modified July 17 12:34 EDT 2024. Contains 374377 sequences. (Running on oeis4.)