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A081375 a(n) is the least number such that A081373[a(n)]=n. 4
1, 2, 6, 12, 30, 42, 72, 78, 84, 90, 190, 216, 222, 228, 234, 252, 270, 540, 546, 570, 630, 738, 744, 770, 792, 858, 900, 924, 930, 990, 1050, 1638, 1710, 1890, 1980, 2100, 2310, 2418, 2442, 2508, 2562, 2574, 2604, 2700, 2772, 2790, 2850, 2970, 3150 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..49.

MATHEMATICA

f[x_] := Count[Table[EulerPhi[j]-EulerPhi[x], {j, 1, x}], 0] t=Table[0, {50}]; Do[s=f[n]; If[s<51&&t[[s]]==0, t[[s]]=n], {n, 1, 4000}]; t

CROSSREFS

Cf. A081373, A081374, A000010, A067004, A008479.

Sequence in context: A237704 A181826 A143176 * A024701 A224532 A179674

Adjacent sequences:  A081372 A081373 A081374 * A081376 A081377 A081378

KEYWORD

nonn

AUTHOR

Labos Elemer, Mar 24 2003

STATUS

approved

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Last modified September 29 02:49 EDT 2020. Contains 337420 sequences. (Running on oeis4.)