login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A230091 Numbers of the form k + wt(k) for exactly two distinct k, where wt(k) = A000120(k) is the binary weight of k. 10
5, 14, 17, 19, 22, 31, 33, 36, 38, 47, 50, 52, 55, 64, 67, 70, 79, 82, 84, 87, 96, 98, 101, 103, 112, 115, 117, 120, 131, 132, 143, 146, 148, 151, 160, 162, 165, 167, 176, 179, 181, 184, 193, 196, 199, 208, 211, 213, 216, 225, 227, 230, 232, 241, 244, 246, 249, 258, 260, 262, 271, 274, 276, 279, 288, 290, 293, 295 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The positions of entries equal to 2 in A228085, or numbers that appear exactly twice in A092391.

Numbers that can be expressed as the sum of distinct terms of the form 2^n+1, n=0,1,... in exactly two ways.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Index entries for Colombian or self numbers and related sequences

EXAMPLE

5 = 3 + 2 = 4 + 1, so 5 is in this list.

MAPLE

# Maple code for A000120, A092391, A228085, A010061, A228088, A230091, A230092

with(LinearAlgebra):

read transforms;

wt := proc(n) local w, m, i; w := 0; m := n; while m > 0 do i := m mod 2; w := w+i; m := (m-i)/2; od; w; end: # A000120

M:=1000;

lis1:=Array(0..M);

lis2:=Array(0..M);

ctmax:=4;

for i from 0 to ctmax do ct[i]:=Array(0..M); od:

for n from 0 to M do

m:=n+wt(n);

lis1[n]:=m;

if (m <= M) then lis2[m]:=lis2[m]+1; fi;

od:

t1:=[seq(lis1[i], i=0..M)]; # A092391

t2:=[seq(lis2[i], i=0..M)]; # A228085

COMPl(t1); # A010061

for i from 1 to M do h:=lis2[i];

if h <= ctmax then ct[h]:=[op(ct[h]), i]; fi; od:

len:=nops(ct[0]); [seq(ct[0][i], i=1..len)]; # A010061 again

len:=nops(ct[1]); [seq(ct[1][i], i=1..len)]; # A228088

len:=nops(ct[2]); [seq(ct[2][i], i=1..len)]; # A230091

len:=nops(ct[3]); [seq(ct[3][i], i=1..len)]; # A230092

PROG

(Haskell)

a230091 n = a230091_list !! (n-1)

a230091_list = filter ((== 2) . a228085) [1..]

-- Reinhard Zumkeller, Oct 13 2013

CROSSREFS

Cf. A000120, A010061, A092391, A228088, A228085, A230058, A230092.

Cf. A227915.

Sequence in context: A196366 A306772 A230058 * A053782 A296692 A102884

Adjacent sequences:  A230088 A230089 A230090 * A230092 A230093 A230094

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, Oct 10 2013

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 16 09:01 EDT 2019. Contains 327093 sequences. (Running on oeis4.)