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A230353 Products of 3 evil primes (A027699) p,q,r, such that numbers p*q, p*r, q*r, and p*q*r are odious (A000069). 2

%I #17 Nov 01 2013 13:22:31

%S 575,1775,2075,2225,2825,3475,6575,8381,8675,8825,8975,8993,10235,

%T 11225,11675,11975,12035,12167,12905,13075,14275,14825,18745,19925,

%U 21575,22881,23943,24389,25325,25775,26765,27575,30189,30925,30981,31433,32223,32675,32975

%N Products of 3 evil primes (A027699) p,q,r, such that numbers p*q, p*r, q*r, and p*q*r are odious (A000069).

%C These numbers are products of 3 evil numbers (A001969) but not represented as products of two evil numbers (A230213).

%H Charles R Greathouse IV and Peter J. C. Moses, <a href="/A230353/b230353.txt">Table of n, a(n) for n = 1..10000</a> (first 500 from Moses)

%e For triple of evil primes {3,29,263} numbers 3*29 = 87, 3*263 = 789, 29*263 = 7627 and 3*29*263 = 22881. Thus 22881 is in the sequence.

%o (PARI) od(n)=hammingweight(n)%2

%o list(lim)=my(v=List(),pq); forprime(p=23,lim\25, if(od(p), next); forprime(q=5,min(lim\(3*p),p), if(od(q) || !od(pq=p*q), next); forprime(r=3,min(lim\pq,q), if(!od(r) && od(q*r) && od(p*r) && od(pq*r), listput(v, pq*r))))); vecsort(Vec(v)) \\ _Charles R Greathouse IV_, Nov 01 2013

%Y Cf. A000069, A001969, A027699, A230213.

%K nonn,base

%O 1,1

%A _Vladimir Shevelev_ and _Peter J. C. Moses_, Oct 16 2013

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Last modified July 15 06:17 EDT 2024. Contains 374324 sequences. (Running on oeis4.)