A231548 Numbers n such that 2*n - 1 < sigma(n) - sigma(n-2).

1680, 2520, 3360, 3780, 3960, 4200, 4680, 5040, 6300, 6720, 7560, 7920, 8820, 9240, 9360, 10080, 10800, 10920, 11340, 11760, 11880, 12600, 13440, 13860, 14040, 15120, 15840, 15960, 16380, 16800, 17280, 17640, 18480, 18900, 19800, 20160, 20520, 21000, 21420

Offset: 1

Author

Jaroslav Krizek, Nov 12 2013

Keywords

• nonn

Comments

Also numbers n such that antisigma(n) < antisigma(n-2), where antisigma(n) = A024816(n) = the sum of the non-divisors of n that are between 1 and n.

Sequence contains anomalous increased frequency of values ending with digit 0.

Conjecture: there are no numbers n such that antisigma(n) < antisigma(n-3).

Examples

			1680 is in sequence because antisigma(1680) = 1406088 < antisigma(1678) = 1406161.
		

Links

• Jaroslav Krizek, Table of n, a(n) for n = 1..228, all terms < 10^5

Crossrefs

Cf. A024816, A213547 (numbers n such that antisigma(n) < antisigma(n-1)).