A231548 -id:A231548 - cp's OEIS frontend

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

Jaroslav Krizek, Nov 12 2013

nonn

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

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

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

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

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

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

A231711 Numbers n such that n > sigma(n) - sigma(n-1).

Original entry on oeis.org

3, 4, 5, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 21, 22, 23, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 81, 82

Offset: 1

Jaroslav Krizek, Nov 12 2013

nonn

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) = A231547.
Numbers n such that antisigma(n) = antisigma(n-1) = A231545.
Complement of union of A231547, A231545 and number 1.

			10 is in sequence because antisigma(10) = 37 > antisigma(9) = 32.

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

Cf. A231545, A231546, A231547, A231548, A024816, A163553.

with(numtheory); A231711:=n->`if`(sigma(n)-sigma(n-1)A231711(n), n=1..100); # Wesley Ivan Hurt, Nov 14 2013

isok(n) = n > sigma(n) - sigma(n-1); \\ Michel Marcus, Nov 14 2013

cp's OEIS Frontend

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

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