A175192 - OEIS

%I #13 Oct 20 2017 18:51:23

%S 1,0,1,1,0,1,1,1,0,0,0,1,1,1,1,0,0,1,0,1,0,0,0,1,0,0,0,1,0,1,1,1,0,0,

%T 0,1,0,1,1,1,0,1,0,1,0,0,0,1,0,0,0,0,0,1,0,1,1,0,0,1,0,1,1,0,0,0,0,1,

%U 0,0,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,0,0,0,0,1,1,0,1,0,0,1,0,1,0,0,0,1,0,1,0

%N a(n) = characteristic function of numbers k such that A000203(m) = k has solution, where A000203(m) = sums of divisors of m.

%C a(n) = 1 if A000203(m) = n for some m, else 0.

%C a(n) = 1 for n such that A054973(n) >= 1. a(n) = 0 for n such that A054973(n) = 0.

%H Antti Karttunen, <a href="/A175192/b175192.txt">Table of n, a(n) for n = 1..65537</a>

%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>

%t nn = 200; t = Union[Select[DivisorSigma[1, Range[nn]], # <= nn &]]; t2 = Table[0, {200}]; t2[[t]] = 1; t2 (* _T. D. Noe_, Jan 24 2012 *)

%o (PARI)

%o up_to = 65537

%o v175192 = vector(up_to);

%o for(k=1, up_to, t=sigma(k); if(t<=up_to, v175192[t] = 1)); \\ See also code in A054973.

%o write_to_bfile(start_offset,vec,bfilename) = { for(n=1, length(vec), write(bfilename, (n+start_offset)-1, " ", vec[n])); }

%o write_to_bfile(1,v175192,"b175192_upto65537.txt");

%o \\ _Antti Karttunen_, Oct 20 2017

%Y Characteristic function of A002191.

%Y Cf. A000203, A054973.

%K nonn

%O 1,1

%A _Jaroslav Krizek_, Mar 01 2010

%E More terms from _Antti Karttunen_, Oct 20 2017