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A109909 a(n) = number of primes of the form k*(n-k)-1. 7
0, 0, 0, 2, 2, 1, 2, 1, 4, 1, 3, 2, 3, 2, 3, 2, 4, 3, 5, 1, 10, 1, 5, 5, 4, 2, 6, 3, 5, 3, 9, 4, 11, 3, 5, 5, 5, 5, 14, 1, 6, 6, 7, 6, 11, 5, 8, 4, 15, 3, 13, 4, 10, 9, 6, 5, 11, 4, 12, 5, 13, 4, 12, 4, 6, 11, 13, 4, 12, 6, 15, 12, 9, 4, 9, 5, 10, 8, 10, 3, 28, 7, 11, 15, 6, 9, 20, 7, 20, 6, 17, 5, 23 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Conjecture: a(n) > 0 for n > 3.

LINKS

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

CROSSREFS

Cf. A109904, A109905, A026728, A109907, A109908.

Sequence in context: A303476 A187201 A262403 * A254573 A144387 A030768

Adjacent sequences:  A109906 A109907 A109908 * A109910 A109911 A109912

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Jul 15 2005

EXTENSIONS

More terms from David Wasserman, Aug 15 2005

STATUS

approved

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Last modified April 19 16:18 EDT 2019. Contains 322282 sequences. (Running on oeis4.)