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A002784
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A problem in parity.
(Formerly M0401 N0154)
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1
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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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).
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PROG
| (PARI) a(n)=if(n<1, 0, sum(k=1, n, if(gcd(n, k) == 1, ((n+k-1)!/(n!*k!))%2)))
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CROSSREFS
| Cf. A050169, A073166.
Sequence in context: A023572 A023570 A011249 * A166029 A049278 A194680
Adjacent sequences: A002781 A002782 A002783 * A002785 A002786 A002787
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| PARI code and more terms from Michael Somos, Jul 19 2002
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