A134608 Composite numbers such that the cube root of the sum of cubes of their prime factors is an integer.

256, 588, 693, 3840, 6561, 14157, 17787, 141960, 178360, 313600, 337365, 350000, 387072, 390625, 407442, 432000, 466560, 531674, 535815, 541310, 664909, 697851, 1044582, 1262056, 1264640, 1299272, 1374327, 1547570, 1608575, 1660360

Offset

1,1

Links

Hieronymus Fischer, Table of n, a(n) for n = 1..300

Example

a(3)=693, since 693=3*3*7*11 and (2*3^3+7^3+11^3)^(1/3)=1728^(1/3)=12.

Mathematica

criQ[n_]:=IntegerQ[Surd[Total[Flatten[Table[#[[1]], #[[2]]]&/@ FactorInteger[ n]]^3], 3]]; Select[Range[1670000], CompositeQ[#] && criQ[#]&] (* Harvey P. Dale, Sep 19 2021 *)

Prog

(PARI) lista(m) = {for (i=2, m, if (! isprime(i), f = factor(i); s = sum (j=1, length(f~), f[j, 1]^3*f[j, 2]); if (ispower(s, 3), print1(i, ", ")); ); ); } \\ Michel Marcus, Apr 14 2013

Crossrefs

Cf. A001597, A025475, A134333, A134344, A134376.

Cf. A134600, A134602, A134605, A134611, A134616, A134618, A134620.

Sequence in context: A206137 A206130 A110297 * A134609 A260065 A329488

Adjacent sequences: A134605 A134606 A134607 * A134609 A134610 A134611

Keyword

nonn

Author

Hieronymus Fischer, Nov 11 2007

Extensions

Minor edits by Hieronymus Fischer, Apr 20 2013

Status

approved