The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A053761 Least positive integer k for which the Jacobi symbol (k|2*n-1) is less than 1, where 2*n-1 is a nonsquare; a(n)=0 if 2*n-1 is a square. 3
 0, 2, 2, 3, 0, 2, 2, 3, 3, 2, 2, 5, 0, 2, 2, 3, 3, 2, 2, 3, 3, 2, 2, 5, 0, 2, 2, 3, 3, 2, 2, 3, 3, 2, 2, 7, 5, 2, 2, 3, 0, 2, 2, 3, 3, 2, 2, 5, 5, 2, 2, 3, 3, 2, 2, 3, 3, 2, 2, 7, 0, 2, 2, 3, 3, 2, 2, 3, 3, 2, 2, 5, 5, 2, 2, 3, 3, 2, 2, 3, 3, 2, 2, 5, 0, 2, 2, 3, 3, 2, 2, 3, 3, 2, 2, 7, 5, 2, 2, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES Steven R. Finch, Mathematical Constants, Cambridge, 2003, pp. 443-448. Paulo Ribenboim, The New Book of Prime Number Records, 3rd ed., Springer-Verlag 1996; Math. Rev. 96k:11112. LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 R. Baillie and S. S. Wagstaff, Lucas pseudoprimes, Math. Comp. 35 (1980) 1391-1417; Math. Rev. 81j:10005 Steven R. Finch, Quadratic Residues [Broken link] Steven R. Finch, Quadratic Residues [From the Wayback machine] FORMULA a(1) = 0; for n > 1, a(n) = (1-A010052((2*n)-1)) * A112046(n-1). - Antti Karttunen, May 10 2017 MAPLE A053761 := proc(n) if issqr(2*n-1) then return 0 ; else for k from 1 do if numtheory[jacobi](k, 2*n-1) < 1 then return k; end if; end do: end if; end proc: seq(A053761(n), n=1..100) ; # R. J. Mathar, Aug 08 2010 MATHEMATICA a[n_] := If[IntegerQ[Sqrt[2*n - 1]], Return[0], For[ k = 1, True, k++, If[ JacobiSymbol[k, 2*n - 1] < 1 , Return[k]]]]; Table[a[n], {n, 1, 100}] (* Jean-François Alcover, Jun 20 2013, after R. J. Mathar *) PROG (PARI) A112046(n) = for(i=1, (2*n), if((kronecker(i, (n+n+1)) < 1), return(i))); A053761(n) = if(issquare((2*n)-1), 0, A112046(n-1)); for(n=1, 10000, write("b053761.txt", n, " ", A053761(n))); \\ Antti Karttunen, May 10 2017 (Scheme) (define (A053761 n) (if (= 1 n) 0 (* (- 1 (A010052 (+ n n -1))) (A112046 (- n 1))))) ;; Antti Karttunen, May 10 2017 CROSSREFS Cf. A010052, A053760, A112046, A112049, A268829. Sequence in context: A290125 A307356 A091426 * A138067 A324348 A125093 Adjacent sequences:  A053758 A053759 A053760 * A053762 A053763 A053764 KEYWORD nonn AUTHOR Steven Finch, Apr 05 2000 EXTENSIONS More terms from R. J. Mathar, Aug 08 2010 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.

Last modified April 16 18:53 EDT 2021. Contains 343050 sequences. (Running on oeis4.)