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A294776 Squarefree products of k primes that are symmetrically distributed around their average. Case k = 6. 3

%I

%S 1616615,3411705,7436429,9408035,10163195,12838371,13037385,13844919,

%T 14969435,19605131,20414121,23783045,24997749,25113935,27568145,

%U 30478565,31473255,32518535,33999455,39946569,43134015,46115135,48215255,50907855,56179409,61558343

%N Squarefree products of k primes that are symmetrically distributed around their average. Case k = 6.

%p with(numtheory): P:=proc(q,h) local a,b,k,n,ok;

%p for n from 2*3*5*7*11*13 to q do if not isprime(n) and issqrfree(n) then a:=ifactors(n)[2];

%p if nops(a)=h then b:=2*add(a[k][1],k=1..nops(a))/nops(a); ok:=1;

%p for k from 1 to trunc(nops(a)/2) do if a[k][1]+a[nops(a)-k+1][1]<>b then ok:=0; break; fi; od; if ok=1 then print(n); fi; fi; fi; od; end: P(10^9,6);

%o (PARI) isok(n, nb=6) = {if (issquarefree(n) && (omega(n)==nb), f = factor(n)[, 1]~; avg = vecsum(f)/#f; for (k=1, #f\2, if (f[k] + f[#f-k+1] != 2*avg, return(0));); return (1););} \\ _Michel Marcus_, Nov 10 2017

%Y Subsequence of A067885.

%Y Cf. A006881 (k=2), A262723 (k=3), A294751 (k=4), A294752 (k=5).

%K nonn

%O 1,1

%A _Paolo P. Lava_, Nov 09 2017

%E More terms from _Giovanni Resta_, Nov 09 2017

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Last modified April 22 08:56 EDT 2019. Contains 322329 sequences. (Running on oeis4.)