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A244799 Number of moduli m such (prime(n) mod m) is odd, where 1 <= m < prime(n). 3
0, 1, 2, 4, 6, 8, 9, 12, 14, 17, 21, 23, 25, 29, 29, 33, 37, 41, 42, 46, 49, 51, 52, 56, 62, 64, 68, 66, 70, 74, 83, 86, 86, 90, 93, 99, 103, 108, 106, 111, 113, 119, 123, 125, 124, 130, 139, 147, 144, 148, 148, 156, 160, 163, 164, 168, 174, 182, 180, 182 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) + A244800(n) = A000040(n) = n-th prime.

LINKS

Clark Kimberling, Table of n, a(n) for n = 1..1000

EXAMPLE

In the following table, mh abbreviates mod(h) and p(n) = prime(n).

n . p(n) . m2 . m3 . m4 . m5 . m6 . m7 . m8 . m9 . m10 . m11 #odd #even

1 . 2 .... 0 .. 0 ........................................... 0 .. 2

2 . 3 .... 0 .. 1 .. 0 ...................................... 1 .. 2

3 . 5 .... 0 .. 1 .. 2 .. 1 .. 0 ............................ 2 .. 3

4 . 7 .... 0 .. 1 .. 1 .. 3 .. 2 .. 1 .. 0 .................. 4 .. 3,

so that A244799 = (0,1,2,4,...) and A244800 = (2,2,3,3,...).

MATHEMATICA

z = 1000; f[n_, m_] := If[OddQ[Mod[Prime[n], m]], 1, 0]

t = Table[f[n, m], {n, 1, z}, {m, 1, Prime[n]}];

Table[Count[t[[k]], 1], {k, 1, z}] (* A244799 *)

CROSSREFS

Cf. A244800, A000040.

Sequence in context: A189170 A138969 A161819 * A316350 A071562 A241562

Adjacent sequences:  A244796 A244797 A244798 * A244800 A244801 A244802

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Jul 06 2014

STATUS

approved

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Last modified November 17 23:26 EST 2019. Contains 329242 sequences. (Running on oeis4.)