A225836 Numbers of form 2^j*(4k+1), j >= 0, k >= 1.

5, 9, 10, 13, 17, 18, 20, 21, 25, 26, 29, 33, 34, 36, 37, 40, 41, 42, 45, 49, 50, 52, 53, 57, 58, 61, 65, 66, 68, 69, 72, 73, 74, 77, 80, 81, 82, 84, 85, 89, 90, 93, 97, 98, 100, 101, 104, 105, 106, 109, 113, 114, 116, 117, 121, 122, 125, 129, 130, 132, 133

Offset: 1

Author

Ralf Stephan, May 16 2013

Keywords

• nonn
• easy

Comments

A091072 without the powers of 2.

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A091067.

Programs

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

Mathematica

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 *)

PARI

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

PARI

is(n)=n>>=valuation(n,2); n%4==1 && n>1 \\ Charles R Greathouse IV, Sep 27 2015

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

Formula

a(n) ~ 2n. - Charles R Greathouse IV, Sep 27 2015