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A266276
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a(n) is the smallest number k such that phi(k) = n*phi(k-1).
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3
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..5.
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EXAMPLE
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a(3) = 7 because 7 is the smallest number k such that phi(k) = n*phi(k-1); phi(7) = 6 =3*phi(6) = 3*2.
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PROG
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(MAGMA) a:=func<n|exists(r){k:k in[2..10^8] | EulerPhi(k) eq n*EulerPhi(k-1)}select r else 0>; [a(n):n in[1..5]]
(PARI) a(n) = my(k=2, epk=1, enk); while ((enk=eulerphi(k)) != n*epk, epk = enk; k++); k; \\ Michel Marcus, Feb 20 2020
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CROSSREFS
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Sequences of numbers n such that phi(n) = k*phi(n-1) for k = 1, 2, 3, 4, 5: {A001274 + 1} for k=1; A171271 = {A050472 + 1} for k=2; A266268 = {A067143 + 1} for k=3; A268126 = {A172314 + 1} for k=4; {A201253 + 1} for k=5.
Cf. A000010 (phi(n)), A266269 (the smallest numbers k such that phi(k) >= n*phi(k-1)).
Sequence in context: A069503 A077524 A238400 * A088252 A334021 A196303
Adjacent sequences: A266273 A266274 A266275 * A266277 A266278 A266279
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KEYWORD
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nonn,more
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AUTHOR
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Jaroslav Krizek, Jan 26 2016
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STATUS
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approved
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