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 A252502 Number of digits of Phi_n(10), or number of digits in base b of Phi_n(b), where Phi is the cyclotomic polynomial. 1
 1, 2, 3, 3, 5, 2, 7, 5, 7, 4, 11, 4, 13, 6, 8, 9, 17, 6, 19, 8, 12, 10, 23, 8, 21, 12, 19, 12, 29, 9, 31, 17, 20, 16, 24, 12, 37, 18, 24, 16, 41, 13, 43, 20, 24, 22, 47, 16, 43, 20, 32, 24, 53, 18, 40, 24, 36, 28, 59, 17, 61, 30, 36, 33, 48, 21, 67, 32, 44, 25, 71, 24 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) = phi(n) if and only if the number of distinct prime factors of n (A001221(n)) is even, a(n) = phi(n) + 1 if and only if the number of distinct prime factors of n (A001221(n)) is odd, where phi is Euler's totient function. LINKS Eric Chen, Table of n, a(n) for n = 1..1000 EXAMPLE Values of phi_n(b) written in base b are #, 11, 111, 101, 11111, #1, 1111111, 10001, 1001001, #0#1, 11111111111, ##01, ..., where # represents b - 1. MATHEMATICA a252502[n_] := Array[Total@DigitCount[Cyclotomic[#, 10]] &, n]; a252502[72] (* Michael De Vlieger, Dec 21 2014 *) CROSSREFS Cf. A000010, A019328, A063672, A206225. Sequence in context: A069461 A329071 A232932 * A063256 A229703 A131320 Adjacent sequences:  A252499 A252500 A252501 * A252503 A252504 A252505 KEYWORD nonn AUTHOR Eric Chen, Dec 17 2014 STATUS approved

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Last modified June 17 00:17 EDT 2021. Contains 345080 sequences. (Running on oeis4.)