A129139 a(n) = number of positive integers which are coprime to n and are <= d(n), where d(n) = A000005(n).

1, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 2, 2, 2, 2, 3, 2, 2, 3, 3, 2, 3, 3, 2, 2, 2, 3, 3, 2, 4, 3, 2, 2, 3, 3, 2, 2, 2, 3, 3, 2, 2, 3, 3, 2, 3, 3, 2, 3, 4, 3, 3, 2, 2, 3, 2, 2, 4, 4, 4, 3, 2, 3, 3, 2, 2, 4, 2, 2, 3, 3, 4, 3, 2, 4, 4, 2, 2, 3, 4, 2, 3, 4, 2, 3, 4, 3, 3, 2, 4, 4, 2, 3, 4, 4, 2, 3, 2, 4, 4

Offset

1,3

Links

Antti Karttunen, Table of n, a(n) for n = 1..16384

Example

d(16) = 5. So a(16) is the number of integers coprime to 16 which are <= 5. There are 3 such integers: 1, 3, 5; so a(16) = 3.

Maple

with(numtheory): a:=proc(n) local ct, j: ct:=0: for j from 1 to tau(n) do if gcd(j, n)=1 then ct:=ct+1 else fi od: ct; end: seq(a(n), n=1..140); # Emeric Deutsch, Apr 02 2007

Prog

(PARI) A129139(n) = sum(k=1, numdiv(n), (1==gcd(k, n))); \\ Antti Karttunen, Apr 01 2021

Crossrefs

Cf. A000005, A129138, A126131, A074919.

Sequence in context: A251139 A195061 A064130 * A032539 A122922 A278570

Adjacent sequences: A129136 A129137 A129138 * A129140 A129141 A129142

Keyword

nonn

Author

Leroy Quet, Mar 30 2007

Extensions

More terms from Emeric Deutsch, Apr 02 2007

Status

approved