A134607 Composite numbers such that the square root of the sum of squares of their prime factors is a prime.
48, 320, 486, 3072, 3150, 6174, 7128, 7650, 10890, 11466, 15000, 18018, 18810, 25578, 27846, 29400, 30240, 39546, 40590, 45056, 45927, 53010, 54600, 55062, 59202, 73440, 75582, 77418, 80910, 85800, 90552, 92106, 95238, 96642, 98838
Offset: 1
Keywords
Examples
a(2)=320, since 320=2*2*2*2*2*2*5 and sqrt(6*2^2+5^2)=sqrt(49)=7.
Links
- Hieronymus Fischer, Table of n, a(n) for n = 1..1000
Crossrefs
Programs
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Mathematica
sspfpQ[n_]:=PrimeQ[Sqrt[Total[Flatten[Table[#[[1]],{#[[2]]}]&/@ FactorInteger[ n]]^2]]]; upto=100000;With[{comps=Complement[ Range[ upto],Prime[ Range[PrimePi[upto]]]]},Select[comps,sspfpQ]] (* Harvey P. Dale, Jul 10 2013 *)
Extensions
Minor edits by Hieronymus Fischer, Apr 19 2013
Comments