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 A131484 Numbers n such that A001414(n) divides n+1 and A001414(n+1) divides n. 1

%I

%S 44,41005,41040,68263,91907,109736,416325,603954,826987,1122407,

%T 1218999,1262079,1533375,1649375,1835584,1935225,1964199,2141888,

%U 2562016,2615799,2649352,3021075,3186000,3554880,3863678,4221536,4655805,4925844,5236153,5273100

%N Numbers n such that A001414(n) divides n+1 and A001414(n+1) divides n.

%C There is remote formal resemblance to amicable pairs.

%H Klaus Brockhaus and Donovan Johnson, <a href="/A131484/b131484.txt">Table of n, a(n) for n = 1..1000</a> (first 126 terms from Klaus Brockhaus)

%e 44 = 2*2*11 has sum of prime factors 15, which divides 44 + 1 = 45; 45 = 3*3*5 has sum of prime factors 11, which divides 44. Hence 44 is in the sequence.

%o (PARI) {m=4700000; s=2; for(n=2, m, f=factor(n+1); t=sum(j=1, matsize(f), f[j, 1]*f[j, 2]); if((n+1)%s==0&&n%t==0, print1(n, ",")); s=t)} /* _Klaus Brockhaus_, Jul 30 2007 */

%Y Cf. A001414 (sum of prime factors of n, with repetition), A063990 (amicable numbers), A130871.

%K nonn

%O 1,1

%A _J. M. Bergot_, Jul 28 2007

%E Edited and extended by _Stefan Steinerberger_ and _Klaus Brockhaus_, Jul 30 2007

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Last modified June 14 21:27 EDT 2021. Contains 345041 sequences. (Running on oeis4.)