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A088820 Numbers n with abundance radius of 8, i.e., abs(sigma(n)-2n) = 8. 0
22, 56, 130, 184, 368, 836, 1012, 2272, 11096, 17816, 18904, 33664, 45356, 70564, 77744, 85936, 91388, 100804, 128768, 254012, 388076, 391612, 527872, 1090912, 2087936, 2291936, 13174976, 17619844, 29465852, 35021696, 45335936, 120888092 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Original definition: Abundance-radius=8, that is Abs[sigma[n]-2n]=8 (either +8 or -8). A045770 from 3rd term complemented by -8 cases.

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

22 is in the sequence since sigma(22) = 1 + 2 + 11 + 22 = 36 = 2*22 - 8.

56 is in the sequence since sigma(56) = 1 + 2 + 4 + 7 + 8 + 14 + 28 + 56 = 120 = 2*56 + 8. - Michael B. Porter, Jul 20 2016

MATHEMATICA

Select[Range[1, 10^6], Abs[DivisorSigma[1, #] - 2 #] == 8 &] (* Vincenzo Librandi, Jul 20 2016 *)

PROG

(PARI) is(n)=abs(sigma(n)-2*n)==8 \\ Use, e.g., select(is, [1..10^5]*2). - M. F. Hasler, Jul 19 2016

(MAGMA) [n: n in [1..2*10^7] | Abs(DivisorSigma(1, n) - 2*n) eq 8]; // Vincenzo Librandi, Jul 20 2016

CROSSREFS

Cf. A045770, A045768, A055708, A077374, A088007-A088012, A088818, A088819.

Cf. A000203 (sigma), A033880 (abundance), A005100 (deficient numbers); A125247 (deficiency 8).

Sequence in context: A303582 A289015 A063302 * A058097 A131878 A019506

Adjacent sequences:  A088817 A088818 A088819 * A088821 A088822 A088823

KEYWORD

nonn

AUTHOR

Labos Elemer, Oct 20 2003

EXTENSIONS

More terms from David Wasserman, Aug 18 2005

Edited by M. F. Hasler, Jul 19 2016

STATUS

approved

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Last modified April 21 19:16 EDT 2021. Contains 343156 sequences. (Running on oeis4.)