A074882 Number of integers in {1, 2, ..., sigma(n)} that are coprime to n.

1, 2, 3, 4, 5, 4, 7, 8, 9, 7, 11, 9, 13, 10, 13, 16, 17, 13, 19, 17, 19, 16, 23, 20, 25, 19, 27, 24, 29, 19, 31, 32, 29, 25, 34, 31, 37, 28, 35, 36, 41, 27, 43, 38, 42, 34, 47, 41, 49, 38, 45, 45, 53, 40, 53, 51, 51, 43, 59, 45, 61, 46, 60, 64, 63, 43, 67, 59, 61, 50, 71, 65, 73

Offset

1,2

Comments

Compare the definition of a(n) to phi(n) = number of integers in {1, 2, ..., n} that are coprime to n.

Links

Table of n, a(n) for n=1..73.

Example

There are four numbers in {1, 2, ..., sigma(4) = 7} that are coprime to 4, i.e. 1, 3, 5, 7. Hence a(4) = 4.

Mathematica

h[n_] := Module[{l}, l = {}; For[i = 1, i <= DivisorSigma[1, n], i++, If[GCD[i, n] == 1, l = Append[l, i]]]; l]; Table[Length[h[i]], {i, 1, 100}]

Crossrefs

Sequence in context: A079881 A349958 A058084 * A273284 A079867 A273290

Adjacent sequences: A074879 A074880 A074881 * A074883 A074884 A074885

Keyword

nonn

Author

Joseph L. Pe, Oct 04 2002

Status

approved