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

Author

Jaroslav Krizek, Nov 12 2013

Keywords

• nonn

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

Examples

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

Links

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

Crossrefs

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

Programs

Mathematica

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

PARI

is(n)=nCharles R Greathouse IV, Jul 14 2024