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A145257 a(n) is the smallest integer > n that is non-coprime to n and has the same number of 0's in its binary representation as n has. 5

%I #25 Sep 08 2022 08:45:38

%S 6,15,10,30,14,63,18,12,12,55,21,247,30,63,34,85,20,57,24,28,26,253,

%T 38,45,28,30,46,1015,55,1023,66,36,36,42,40,185,42,45,48,205,44,215,

%U 50,51,54,14335,69,56,52,54,56,159,57,95,77,60,60,767,87,4087,126,255,130,80

%N a(n) is the smallest integer > n that is non-coprime to n and has the same number of 0's in its binary representation as n has.

%H Rémy Sigrist, <a href="/A145257/b145257.txt">Table of n, a(n) for n = 2..10000</a>

%H Rémy Sigrist, <a href="/A145257/a145257.gp.txt">PARI program for A145257</a>

%t a[n_] := Block[{},i = n + 1; While[GCD[i, n] == 1 || Not[DigitCount[n, 2, 0] == DigitCount[i, 2, 0]], i++ ]; i]; Table[a[n], {n, 2, 100}] (* _Stefan Steinerberger_, Oct 17 2008 *)

%o (PARI) See Links section.

%o (PARI) a(n) = {my(m = n+1, nb = #binary(n) - hammingweight(n)); while (!((gcd(m, n) > 1) && (nb == #binary(m) - hammingweight(m))), m++); m;} \\ _Michel Marcus_, Feb 06 2020

%o (Magma) a:=[]; for n in [2..70] do k:=n+1; while Gcd(n,k) eq 1 or Multiplicity(Intseq(n,2),0) ne Multiplicity(Intseq(k,2),0) do k:=k+1; end while; Append(~a,k); end for; a; // _Marius A. Burtea_, Feb 06 2020

%Y Cf. A023416 (number of 0's in binary expansion of n).

%Y Cf. A140977, A145254, A145255, A145256.

%K base,nonn

%O 2,1

%A _Leroy Quet_, Oct 05 2008

%E More terms from _Stefan Steinerberger_, Oct 17 2008

%E a(58)-a(64) from _Ray Chandler_, Jun 20 2009

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Last modified March 28 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)