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A002784 A problem in parity.
(Formerly M0401 N0154)
1

%I M0401 N0154 #19 Oct 20 2023 21:12:44

%S 1,1,1,2,3,1,1,4,5,1,3,1,3,1,1,8,15,3,7,4,5,2,3,3,6,2,3,2,3,1,1,16,19,

%T 7,10,5,15,4,5,7,15,3,7,4,5,2,3,5,13,3,5,4,7,1,3,3,5,2,3,1,3,1,1,32,

%U 47,11,31,14,21,6,15,11,31,7,9,7,12,3,7,12,21,7,15,4,11,4,5,7,15,2,7,4,5

%N A problem in parity.

%D H. Gupta, On a problem in parity, Indian J. Math., 11 (1969), 157-163. MR0260659

%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H H. Gupta, <a href="/A002783/a002783_1.pdf">On a problem in parity</a>, Indian J. Math., 11 (1969), 157-163. [Annotated scanned copy]

%o (PARI) a(n)=if(n<1,0,sum(k=1,n,if(gcd(n,k) == 1,((n+k-1)!/(n!*k!))%2))) /* _Michael Somos_, Jul 19 2002 */

%Y Cf. A050169, A073166.

%K nonn

%O 1,4

%A _N. J. A. Sloane_

%E More terms from _Michael Somos_, Jul 19 2002

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