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A072022 Smallest x so that the number of nonprimes (i.e. 1 and composites) in the reduced residue set (RSS(n)) of n equals n. 3
1, 5, 7, 15, 26, 11, 13, 38, 102, 17, 19, 25, 0, 23, 35, 144, 74, 198, 29, 31, 75, 57, 104, 94, 37, 55, 69, 41, 43, 118, 0, 47, 81, 128, 87, 134, 53, 93, 480, 146, 77, 59, 61, 117, 111, 166, 172, 67, 250, 91, 71, 73, 350, 194, 129, 202, 79, 206, 212, 83, 214, 153, 218 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..63.

FORMULA

a(n)=Min{x; A048864(x)=n}; a(n)=0 if no such number exists.

EXAMPLE

n = 15: RRS[15] = {1,2,4,7,8,11,13,14} of which nonprimes = cRRS[15] = {1,4,8,14}, i.e. 4 terms; since 15 is smallest such number, so a(4) = 15. a(m) = 0 for m = {13,31,70,119,189,210,235,236}

MATHEMATICA

f[x_] := EulerPhi[x]-PrimePi[x]+Length[FactorInteger[x]] t=Table[0, {256}]; Do[s=f[n]; If[s<257&&t[[s]]==0, t[[s]]=n], {n, 3, 1000000}]; t

CROSSREFS

Cf. A048864, A072023.

Sequence in context: A068580 A110994 A015833 * A003429 A076860 A067589

Adjacent sequences:  A072019 A072020 A072021 * A072023 A072024 A072025

KEYWORD

nonn

AUTHOR

Labos Elemer, Jun 06 2002

STATUS

approved

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Last modified September 20 23:09 EDT 2014. Contains 247020 sequences.