A329204 - OEIS

A329204

Number of integers less than n having at least as many totatives as n.

0, 1, 0, 1, 0, 3, 0, 2, 1, 4, 0, 6, 0, 4, 2, 3, 0, 8, 0, 6, 3, 5, 0, 10, 1, 6, 3, 8, 0, 16, 0, 7, 4, 9, 2, 15, 0, 9, 4, 14, 0, 21, 0, 10, 7, 9, 0, 21, 2, 15, 5, 11, 0, 22, 5, 14, 7, 11, 0, 33, 0, 12, 10, 12, 3, 29, 0, 15, 6, 26, 0, 28, 0, 16, 13, 18, 4, 34, 0, 24, 7, 17

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OFFSET

1,6

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (first 2000 terms from Joshua Oliver)

Wikipedia, Totative.

EXAMPLE

a(6) = 3, because 6 has 2 totatives and there are 3 integers less than 6 with 2 or more totatives: 3 with 2 totatives, 4 with 2 totatives, and 5 with 4 totatives.

MATHEMATICA

Table[Length[Select[Range[n-1], EulerPhi[#]>=EulerPhi[n]&]], {n, 1, 100}]

PROG

(PARI) a(n) = sum(k=1, n-1, eulerphi(k) >= eulerphi(n)); \\ Michel Marcus, Nov 22 2019

(PARI) first(n)=my(u=vectorsmall(n), v=vector(n)); forfactored(f=1, n, u[f[1]]=eulerphi(f)); for(i=1, n, v[i]=sum(j=1, i-1, u[j]>=u[i])); v \\ Charles R Greathouse IV, Dec 11 2019

CROSSREFS

Cf. A000010.

Sequence in context: A317922 A337320 A194808 * A375493 A268464 A165066

Adjacent sequences: A329201 A329202 A329203 * A329205 A329206 A329207

KEYWORD

nonn,look

AUTHOR

Joshua Oliver, Nov 22 2019

STATUS

approved