

A134605


Composite numbers such that the square root of the sum of squares of their prime factors (with multiplicity) is an integer.


20



16, 48, 81, 320, 351, 486, 512, 625, 1080, 1260, 1350, 1375, 1792, 1836, 2070, 2145, 2175, 2401, 2730, 2772, 3072, 3150, 3510, 4104, 4305, 4625, 4650, 4655, 4998, 5880, 6000, 6174, 6545, 7098, 7128, 7182, 7650, 7791, 7889, 7956, 9030, 9108, 9295, 9324
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OFFSET

1,1


LINKS

Hieronymus Fischer, Table of n, a(n) for n = 1..10000


EXAMPLE

a(2)=48 since 48=2*2*2*2*3 and sqrt(4*2^2+3^2)=sqrt(25)=5.


PROG

(PARI) is(n)=my(f=factor(n)); issquare(sum(i=1, #f~, f[i, 1]^2*f[i, 2])) && !isprime(n) && n>1 \\ Charles R Greathouse IV, Apr 29 2015


CROSSREFS

Cf. A001597, A025475, A134333, A134344, A134376, A134600, A134602, A134608, A134611, A134616, A134618, A134620.
Sequence in context: A069084 A084112 A050428 * A035008 A189972 A023648
Adjacent sequences: A134602 A134603 A134604 * A134606 A134607 A134608


KEYWORD

nonn


AUTHOR

Hieronymus Fischer, Nov 11 2007


STATUS

approved



