cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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

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%I A134608 #13 Sep 19 2021 17:03:22
%S A134608 256,588,693,3840,6561,14157,17787,141960,178360,313600,337365,350000,
%T A134608 387072,390625,407442,432000,466560,531674,535815,541310,664909,
%U A134608 697851,1044582,1262056,1264640,1299272,1374327,1547570,1608575,1660360
%N A134608 Composite numbers such that the cube root of the sum of cubes of their prime factors is an integer.
%H A134608 Hieronymus Fischer, <a href="/A134608/b134608.txt">Table of n, a(n) for n = 1..300</a>
%e A134608 a(3)=693, since 693=3*3*7*11 and (2*3^3+7^3+11^3)^(1/3)=1728^(1/3)=12.
%t A134608 criQ[n_]:=IntegerQ[Surd[Total[Flatten[Table[#[[1]],#[[2]]]&/@ FactorInteger[ n]]^3],3]]; Select[Range[1670000],CompositeQ[#] && criQ[#]&] (* _Harvey P. Dale_, Sep 19 2021 *)
%o A134608 (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
%Y A134608 Cf. A001597, A025475, A134333, A134344, A134376.
%Y A134608 Cf. A134600, A134602, A134605, A134611, A134616, A134618, A134620.
%K A134608 nonn
%O A134608 1,1
%A A134608 _Hieronymus Fischer_, Nov 11 2007
%E A134608 Minor edits by _Hieronymus Fischer_, Apr 20 2013