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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A281131 First appearance of 2^n in A281130. 3
1, 3, 7, 13, 23, 41, 98, 223, 437, 699, 1213, 2624, 4674, 11163, 21300, 40858, 73977, 148591, 297394, 567076, 1100738, 2243474, 4340628, 8726122, 17397270, 34701556, 68372147, 136254352, 271069771, 546613630, 1088921640, 2163138108, 4334318825 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Conjecture: a(n) ~ 2^n.

LINKS

Table of n, a(n) for n=0..32.

Rok Cestnik, C program (utilizing hard drive memory)

EXAMPLE

a(1) = 3 because A281130(3) = 2^1 and A281130(i) != 2^1 for i < 3.

a(2) = 7 because A281130(7) = 2^2 and A281130(i) != 2^2 for i < 7.

MATHEMATICA

a[n_] := a[n] = If[a[n - 2] < a[n - 1], a[n - 1 - a[n - 1]], 2 a[n - 1]]; a[1] = a[2] = 1; Function[w, Function[e, First /@ Lookup[w, 2^e]]@ Range[0, Log2@ Max@ Keys@ w]]@ PositionIndex@ Array[a, 10^7] (* Michael De Vlieger, Jan 21 2017, Version 10. *)

PROG

(C)

#include<stdio.h>

#include<stdlib.h>

int main(void){

   int N = 1000000000;

   int *a = (int*)malloc((N+1)*sizeof(int));

   int max = 1;

   int maxindex = 1;

   a[1] = 1;

   a[2] = 1;

   for(int i = 2; i < N; ++i){

      if(a[i-1] < a[i]) a[i+1] = a[i-a[i]];

      else a[i+1] = 2*a[i];

      if(a[i+1] > max){

         max = a[i+1];

         printf("%d %d\n", maxindex, i+1);

         maxindex++;

      }

   }

   return 0;

}

CROSSREFS

Cf. A281130, A291598.

Sequence in context: A061761 A081494 A161909 * A173168 A048462 A048465

Adjacent sequences:  A281128 A281129 A281130 * A281132 A281133 A281134

KEYWORD

nonn,hard

AUTHOR

Rok Cestnik, Jan 15 2017

EXTENSIONS

a(31)-a(32) from Rok Cestnik, Aug 27 2017

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 22 05:47 EDT 2019. Contains 327287 sequences. (Running on oeis4.)