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Number of primes p such that n divided by p leaves a 1 or a composite (nonzero) remainder.

7

`%I #5 Dec 05 2013 19:55:21
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`%S 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,
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`%T 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,
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`%U 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
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`%N Number of primes p such that n divided by p leaves a 1 or a composite (nonzero) remainder.
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`%e a(7) = 2: there are 2 primes viz. 2,3 which leave a remainder 1 on dividing 7.
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`%t Table[Count[PrimeQ[DeleteCases[Table[Mod[w, Prime[j]], {j, 1, PrimePi[w]}], 0]], False], {w, 1, 256}]
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`%Y Cf. A072530.
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`%K nonn
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`%O 1,7
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`%A _Amarnath Murthy_, Aug 01 2002
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`%E More terms from _Labos Elemer_, Aug 02 2002
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