A002784 A problem in parity.
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, 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, 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
Offset: 1
Keywords
References
- H. Gupta, On a problem in parity, Indian J. Math., 11 (1969), 157-163. MR0260659
- N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
- N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Links
- H. Gupta, On a problem in parity, Indian J. Math., 11 (1969), 157-163. [Annotated scanned copy]
Programs
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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 */
Extensions
More terms from Michael Somos, Jul 19 2002