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URL: https://oeis.org/A072927

⇱ A072927 - OEIS

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A072927
a(n) = minimum value of abs(n-phi(x)), x>0.
1
0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 0, 1, 2, 1, 0, 1, 2, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 0, 1, 2, 3, 2, 1, 0, 1, 0, 1, 0, 1, 0, 1, 2, 1, 0, 1, 2, 1, 0, 1, 2, 1, 0, 1, 2, 1, 0
OFFSET
1,14
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Sean A. Irvine)
FORMULA
a(A002202(n)) = 0.
It seems that Sum_{k=1..n} a(k) is asymptotic to C*n*log(n) with C = 0.15... .
PROG
(PARI) a(n) = if(invphiNum(n) > 0, return(0)); for(k = 1, n-1, forstep(isign = -1, 1, 2, if(invphiNum(n + isign*k) > 0, return(k)))); \\ Amiram Eldar, Apr 18 2025, using Max Alekseyev's invphi.gp (see links).
CROSSREFS
Sequence in context: A123737 A083037 A247477 * A307194 A331218 A120086
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Aug 11 2002
STATUS
approved