A060991 a(n) is the smallest positive integer c such that the equation A049820(x) = c has exactly n solutions.

7, 2, 1, 6, 22, 838, 17638, 192520, 3240114, 219476872, 2146772872, 24443168392

Offset

0,1

Comments

Essentially same as A236565, except here for n=2 we have a(2) = 1 instead of A236565(2) = 0, because this sequence requires its terms to be strictly positive. - Antti Karttunen, Oct 09 2015

Links

Table of n, a(n) for n=0..11.

Example

The solution sets of smallest values of x-d(x) deviations with 1, 2, 3, 4, 5, 6 terms are as follows: {6}, {3, 4}, {9, 10, 12}, {25, 26, 28, 30}, {841, 842, 844, 848, 850}, {17642, 17648, 17650, 17654, 17658, 17670}. Thus difference x-d(x) for x={25, 26, 28, 30} with d(x)={3, 4, 6, 8} divisors is equally 22, so a(4)=22.

Mathematica

s = Array[# - DivisorSigma[0, #] &, {20000}]; t = Length@ Position[s, #] & /@ Range@ Max@ s; Table[FirstPosition[t, n], {n, 0, 6}] // Flatten (* Michael De Vlieger, Oct 09 2015 *)

Crossrefs

Cf. A000005, A049820, A045765, A049816, A236565.

Sequence in context: A010140 A222067 A154020 * A120455 A377813 A268895

Adjacent sequences: A060988 A060989 A060990 * A060992 A060993 A060994

Keyword

more,nonn

Author

Labos Elemer, May 11 2001

Extensions

a(9)-a(11) from Donovan Johnson, Jan 08 2009

Status

approved