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A002784 A problem in parity.
(Formerly M0401 N0154)
1
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; text; internal format)
OFFSET

1,4

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

Table of n, a(n) for n=1..93.

H. Gupta, On a problem in parity, Indian J. Math., 11 (1969), 157-163. [Annotated scanned copy]

PROG

(PARI) a(n)=if(n<1, 0, sum(k=1, n, if(gcd(n, k) == 1, ((n+k-1)!/(n!*k!))%2)))

CROSSREFS

Cf. A050169, A073166.

Sequence in context: A214690 A238878 A011249 * A276010 A166029 A049278

Adjacent sequences:  A002781 A002782 A002783 * A002785 A002786 A002787

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

PARI code and more terms from Michael Somos, Jul 19 2002

STATUS

approved

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Last modified October 20 20:24 EDT 2019. Contains 328273 sequences. (Running on oeis4.)