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 A038189 Bit to left of least significant 1-bit in binary expansion of n. 21
 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Characteristic function of A091067. Image, under the coding i -> floor(i/2), of the fixed point, starting with 0, of the morphism 0 -> 01, 1 -> 02, 2 -> 32, 3 -> 31. - Jeffrey Shallit, May 15 2016 REFERENCES Jean-Paul Allouche and Jeffrey O. Shallit, Automatic sequences, Cambridge, 2003, sect. 5.1.6 LINKS Ivan Panchenko, Table of n, a(n) for n = 0..10000 Michael Gilleland, Some Self-Similar Integer Sequences FORMULA a(0) = 0, a(2*n) = a(n) for n>0, a(4*n+1) = 0, a(4*n+3) = 1. G.f.: Sum_{k>=0} t^3/(1-t^4), where t=x^2^k. Parity of A025480. a(n) = 1/2 * (1 - (-1)^A025480(n)). - Ralf Stephan, Jan 04 2004 a(n) = 1 if Kronecker(-n,m)=Kronecker(m,n) for all m, otherwise a(n)=0. - Michael Somos, Sep 22 2005 a(n) = 1 iff A164677(n) < 0. - M. F. Hasler, Aug 06 2015 EXAMPLE a(6) = 1 since 6 = 110 and bit before rightmost 1 is a 1. MAPLE A038189 := proc(n)     option remember;     if n = 0 then         0 ;     elif type(n, 'even') then         procname(n/2) ;     elif modp(n, 4) = 1 then         0 ;     else         1 ;     end if; end proc: seq(A038189(n), n=0..100) ; # R. J. Mathar, Mar 30 2018 MATHEMATICA f[n_] := Block[{id2 = Join[{0}, IntegerDigits[n, 2]]}, While[ id2[[-1]] == 0, id2 = Most@ id2]; id2[[-2]]]; f[0] = 0; Array[f, 105, 0] (* Robert G. Wilson v, Apr 14 2009 and fixed Feb 27 2014 *) f[n_] := f[n] = Switch[Mod[n, 4], 0, f[n/2], 1, 0, 2, f[n/2], 3, 1]; f[0] = 0; Array[f, 105, 0] (* Robert G. Wilson v, Apr 14 2009, fixed Feb 27 2014 *) PROG (C) int a(int n) { return (n & ((n&-n)<<1)) ? 1 : 0; } /* from Russ Cox */ (PARI) a(n) = if(n<1, 0, ((n/2^valuation(n, 2)-1)/2)%2) /* Michael Somos, Sep 22 2005 */ (PARI) a(n) = if(n<3, 0, prod(m=1, n, kronecker(-n, m)==kronecker(m, n))) /* Michael Somos, Sep 22 2005 */ (PARI) A038189(n)=bittest(n, valuation(n, 2)+1) \\ M. F. Hasler, Aug 06 2015 (PARI) a(n)=my(h=bitand(n, -n)); n=bitand(n, h<<1); n!=0; \\ Joerg Arndt, Apr 09 2021 (Magma) function a (n)   if n eq 0 then return 0; // alternatively,  return 1;   else while IsEven(n) do n := n div 2; end while; end if;   return n div 2 mod 2; end function;   nlo := 0; nhi := 32;   [a(n) : n in [nlo..nhi] ]; //  Fred Lunnon, Mar 27 2018 (Python) def A038189(n):     s = bin(n)[2:]     m = len(s)     i = s[::-1].find('1')     return int(s[m-i-2]) if m-i-2 >= 0 else 0 # Chai Wah Wu, Apr 08 2021 CROSSREFS Cf. A038190. A014707(n)=a(n+1). A014577(n)=1-a(n+1). The following are all essentially the same sequence: A014577, A014707, A014709, A014710, A034947, A038189, A082410. - N. J. A. Sloane, Jul 27 2012 Related sequences A301848, A301849, A301850. - Fred Lunnon, Mar 27 2018 Sequence in context: A288508 A262588 A234577 * A072783 A353478 A353555 Adjacent sequences:  A038186 A038187 A038188 * A038190 A038191 A038192 KEYWORD nonn,easy AUTHOR Fred Lunnon, Dec 11 1999 EXTENSIONS More terms from David W. Wilson Definition corrected by Russ Cox and Ralf Stephan, Nov 08 2004 STATUS approved

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Last modified May 19 11:15 EDT 2022. Contains 353833 sequences. (Running on oeis4.)