A231547 Numbers n such that n < sigma(n) - sigma(n-1).

12, 18, 20, 24, 30, 36, 42, 48, 54, 60, 72, 80, 84, 90, 96, 102, 104, 108, 114, 120, 126, 132, 138, 140, 144, 150, 156, 160, 162, 168, 174, 180, 192, 198, 200, 204, 210, 216, 224, 228, 234, 240, 252, 258, 260, 264, 270, 272, 276, 280, 282, 288, 294, 300, 306

Offset

1,1

Comments

Also numbers n such that antisigma(n) < antisigma(n-1), where antisigma(n) = A024816(n) = the sum of the non-divisors of n that are between 1 and n.

Numbers n such that A163553(n-1) < 0.

Numbers n such that antisigma(n) > antisigma(n-1) = A231711.

Numbers n such that antisigma(n) = antisigma(n-1) = A231545.

Complement of union of A231711, A231545 and number 1.

Does this sequence have a density? - Charles R Greathouse IV, Jul 14 2024

Links

Jaroslav Krizek, Table of n, a(n) for n = 1..1000

Example

12 is in sequence because antisigma(12) = 50 < antisigma(11) = 54.

Mathematica

Select[Range[350], #<(DivisorSigma[1, #]-DivisorSigma[1, #-1])&] (* Harvey P. Dale, May 26 2016 *)

Prog

(PARI) is(n)=n<sigma(n)-sigma(n-1) \\ Charles R Greathouse IV, Jul 14 2024

Crossrefs

Cf. A231545, A231546, A231711, A231548, A024816, A163553.

Sequence in context: A173490 A005101 A124626 * A290141 A087245 A342100

Adjacent sequences: A231544 A231545 A231546 * A231548 A231549 A231550

Keyword

nonn

Author

Jaroslav Krizek, Nov 12 2013

Status

approved