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

Author

N. J. A. Sloane

Keywords

• nonn

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]

Crossrefs

Cf. A050169, A073166.

Programs

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