A225836 - OEIS

%I #15 Sep 08 2022 08:46:05

%S 5,9,10,13,17,18,20,21,25,26,29,33,34,36,37,40,41,42,45,49,50,52,53,

%T 57,58,61,65,66,68,69,72,73,74,77,80,81,82,84,85,89,90,93,97,98,100,

%U 101,104,105,106,109,113,114,116,117,121,122,125,129,130,132,133

%N Numbers of form 2^j*(4k+1), j >= 0, k >= 1.

%C A091072 without the powers of 2.

%H Charles R Greathouse IV, <a href="/A225836/b225836.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) ~ 2n. - _Charles R Greathouse IV_, Sep 27 2015

%t mx = 149; t = {}; Do[n = 2^j (4 k + 1); If[n <= mx, AppendTo[t, n]], {j, 0, Log[2, mx]}, {k, mx/4}]; Union[t] (* _T. D. Noe_, May 16 2013 *)

%o (PARI) for(n=1,200,t=n/2^valuation(n,2);if(t>1&&(t%4==1),print1(n,",")))

%o (PARI) is(n)=n>>=valuation(n,2); n%4==1 && n>1 \\ _Charles R Greathouse IV_, Sep 27 2015

%o (PARI) list(lim)=my(v=List(),t); forstep(n=5,lim,4, listput(v,t=n); while((t<<=1)<=lim, listput(v,t))); Set(v) \\ _Charles R Greathouse IV_, Sep 27 2015

%o (Magma) [n: n in [1..200] | d gt 1 and IsOne(d mod 4) where d is n div 2^Valuation(n,2)]; // _Bruno Berselli_, May 16 2013

%Y Cf. A091067.

%K nonn,easy

%O 1,1

%A _Ralf Stephan_, May 16 2013