A144862 - OEIS

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A144862

Composite numbers n such that sqrt(n) > f(n), where f(n) = 2 * rad(n) if 4 divides n and rad(n) otherwise.

27, 32, 54, 64, 81, 125, 128, 162, 192, 216, 243, 250, 256, 288, 324, 343, 375, 384, 405, 432, 486, 500, 512, 567, 576, 625, 640, 648, 675, 686, 729, 768, 800, 864, 896, 972, 1000, 1024, 1029, 1125, 1152, 1215, 1250, 1280, 1296, 1323, 1331, 1350, 1372, 1458

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OFFSET

1,1

COMMENTS

Subset of A144100.

LINKS

Table of n, a(n) for n=1..50.

PROG

(PARI) rad(n) = local(p); p=factor(n)[, 1]; prod(i=1, length(p), p[i]) ;

ff(n) = if ((n % 4)==0 , 2*rad(n), rad(n)); isok(n) = (n != 1) && (! isprime(n)) && (n > ff(n)^2); \\ Michel Marcus, Aug 09 2013

CROSSREFS

Cf. A000040, A007947, A144100.