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A070275 Numbers k such that the sum of the digits of k equals the sum of the prime divisors of k. 8

%I #27 May 27 2018 01:41:03

%S 2,3,5,7,84,160,250,336,468,735,936,975,1344,1375,1408,1600,1694,1872,

%T 2352,2401,2500,2625,2808,3744,3920,4116,4913,5145,5616,6084,6318,

%U 7296,7497,7695,8424,8624,8664,8704,9126,9639,10240,12168,12636,12675,14896

%N Numbers k such that the sum of the digits of k equals the sum of the prime divisors of k.

%C If k=10^s*m is a term of the sequence where s > 0 and gcd(m,10)=1, then for each positive integer j, 10^j*m is in the sequence, because the sum of the digits of 10^j*k equals the sum of the digits of k and the sum of the distinct prime factors of 10^j*k equals the sum of the distinct prime factors of k. Also it is obvious that m isn't in the sequence. [_Jahangeer Kholdi_, Oct 07 2013]

%H Giovanni Resta, <a href="/A070275/b070275.txt">Table of n, a(n) for n = 1..10000</a>

%t Rest[Select[Range[20000],Total[Transpose[FactorInteger[#]][[1]]] == Total[ IntegerDigits[#]] &]] (* Harvey P. Dale, Dec 15 2010 *)

%o (PARI) isok(n) = sumdigits(n) == vecsum(factor(n)[,1]); \\ _Michel Marcus_, May 27 2018

%Y Cf. A008472, A057531, A057532, A050689, A070274, A063737, A067077, A285494.

%K easy,nonn,base

%O 1,1

%A _Benoit Cloitre_, May 09 2002

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)