A090128 Distinct values of sigma(k), the sum of divisors, in order of appearance as k grows.

1, 3, 4, 7, 6, 12, 8, 15, 13, 18, 28, 14, 24, 31, 39, 20, 42, 32, 36, 60, 40, 56, 30, 72, 63, 48, 54, 91, 38, 90, 96, 44, 84, 78, 124, 57, 93, 98, 120, 80, 168, 62, 104, 127, 144, 68, 126, 195, 74, 114, 140, 186, 121, 224, 108, 132, 180, 234, 112, 128, 252, 171, 156, 217

Offset: 1

Author

Labos Elemer, Jan 16 2004

Keywords

• nonn
• easy

Comments

Constructed by reading A000203 and deleting values that already appeared earlier: A000203(15)=24 is dropped because equal to A000203(14). A000203(17)=18 is dropped because equal to A000203(10) etc. - R. J. Mathar, May 27 2024

Links

• Giovanni Resta, Table of n, a(n) for n = 1..10000
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A002191 (terms in ascending order).

Cf. A053212, A090127.

Programs

Mathematica

t = Table[DivisorSigma[1, w], {w, 100}]; u = Union[t]; uu = Union@ Table[ Min[ Flatten[ Position[t, u[[j]]]]], {j, Length[u]}]; Table[ t[[uu[[j]]]], {j, Length[uu]}]
DeleteDuplicates[DivisorSigma[1,Range[100]]] (* Harvey P. Dale, Dec 01 2018 *)