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A294776 Squarefree products of k primes that are symmetrically distributed around their average. Case k = 6. 3
1616615, 3411705, 7436429, 9408035, 10163195, 12838371, 13037385, 13844919, 14969435, 19605131, 20414121, 23783045, 24997749, 25113935, 27568145, 30478565, 31473255, 32518535, 33999455, 39946569, 43134015, 46115135, 48215255, 50907855, 56179409, 61558343 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..26.

MAPLE

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

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

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

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);

PROG

(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

CROSSREFS

Subsequence of A067885.

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

Sequence in context: A235174 A234410 A069374 * A103793 A064117 A173428

Adjacent sequences:  A294773 A294774 A294775 * A294777 A294778 A294779

KEYWORD

nonn

AUTHOR

Paolo P. Lava, Nov 09 2017

EXTENSIONS

More terms from Giovanni Resta, Nov 09 2017

STATUS

approved

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Last modified March 21 18:59 EDT 2019. Contains 321382 sequences. (Running on oeis4.)