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 A266276 a(n) is the smallest number k such that phi(k) = n*phi(k-1). 3
 2, 3, 7, 1261, 11242771 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 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. PROG (MAGMA) a:=func; [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 CROSSREFS 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 KEYWORD nonn,more AUTHOR Jaroslav Krizek, Jan 26 2016 STATUS approved

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Last modified January 23 05:32 EST 2021. Contains 340384 sequences. (Running on oeis4.)