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A072531
Number of primes p such that n divided by p leaves a 1 or a composite (nonzero) remainder.
7
0, 0, 1, 1, 1, 1, 2, 1, 2, 1, 3, 1, 3, 2, 3, 2, 3, 2, 5, 3, 5, 3, 5, 2, 6, 3, 6, 3, 6, 3, 7, 6, 5, 6, 7, 3, 7, 5, 8, 4, 8, 4, 10, 6, 8, 7, 9, 6, 10, 7, 9, 8, 11, 6, 11, 9, 10, 7, 11, 5, 14, 9, 11, 9, 11, 8, 15, 9, 13, 8, 14, 8, 14, 12, 14, 11, 15, 9, 15, 11, 14, 12, 18, 10, 16, 14, 15, 13, 16, 9
OFFSET
1,7
EXAMPLE
a(7) = 2: there are 2 primes viz. 2,3 which leave a remainder 1 on dividing 7.
MATHEMATICA
Table[Count[PrimeQ[DeleteCases[Table[Mod[w, Prime[j]], {j, 1, PrimePi[w]}], 0]], False], {w, 1, 256}]
CROSSREFS
Cf. A072530.
Sequence in context: A126131 A343332 A138012 * A025818 A324938 A362181
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Aug 01 2002
EXTENSIONS
More terms from Labos Elemer, Aug 02 2002
STATUS
approved