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A061346 Odd numbers that are neither primes nor prime powers. 10

%I

%S 15,21,33,35,39,45,51,55,57,63,65,69,75,77,85,87,91,93,95,99,105,111,

%T 115,117,119,123,129,133,135,141,143,145,147,153,155,159,161,165,171,

%U 175,177,183,185,187,189,195,201,203,205,207,209,213,215,217,219,221

%N Odd numbers that are neither primes nor prime powers.

%C Odd leg of more than one primitive Pythagorean triangles. For smallest odd leg common to 2^n PPTs, see A070826. - _Lekraj Beedassy_, Jul 12 2006

%C Numbers that can be factored by Shor's algorithm. - _Charles R Greathouse IV_, Mar 05 2012

%H Charles R Greathouse IV, <a href="/A061346/b061346.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) ~ 2n. - _Charles R Greathouse IV_, Aug 20 2012

%p select(t -> nops(ifactors(t)[2]) > 1, [seq(2*i+1,i=1..1000)]); # _Robert Israel_, Dec 14 2014

%t Select[Range[1, 249, 2], Length[FactorInteger[#]] > 1 &] (* _Alonso del Arte_, Jan 30 2012 *)

%t Select[ Range[1, 475, 2], PrimeNu@# > 1 &] (* _Robert G. Wilson v_, Dec 12 2014 *)

%o (ARIBAS): for k := 3 to 253 by 2 do ar := factorlist(k); if ar[0] < ar[length(ar)-1] then write(k," ") end; end;

%o (PARI) is(n)=ispower(n,,&n);n%2&&!isprime(n)&&n>1 \\ _Charles R Greathouse IV_, Jan 30 2012

%o (PARI) is(n)=n%2 && !isprimepower(n) && n>1 \\ _Charles R Greathouse IV_, May 06 2016

%o (PARI) count(x)=if(x<9, 0, (x\=1) - sum(k=1,logint(x,3), primepi(sqrtnint(x,k)) - 1) - x\2 - 1) \\ _Charles R Greathouse IV_, Mar 06 2018

%Y Subsequence of A056911.

%Y Cf. A061345.

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_, Jun 08 2001

%E More terms from _Klaus Brockhaus_, Jun 10 2001

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Last modified July 23 12:06 EDT 2021. Contains 346259 sequences. (Running on oeis4.)