A111667 -id:A111667 - cp's OEIS frontend

A111646 Subtracted divisor in admirable numbers.

2, 1, 6, 6, 5, 6, 6, 4, 6, 2, 6, 28, 2, 6, 1, 6, 60, 6, 28, 6, 6, 6, 28, 39, 6, 6, 90, 6, 28, 6, 6, 28, 6, 4, 6, 6, 6, 1, 6, 28, 6, 28, 6, 6, 6, 6, 6, 28, 1, 6, 336, 6, 6, 6, 28, 6, 6, 4, 28, 6, 6, 6, 15, 6, 16, 6, 28, 6, 6, 6, 6, 28, 6, 6, 6, 28, 6, 28, 6, 6, 28, 6, 6, 6, 6, 28, 496, 8, 6, 6, 6, 6

Offset: 1

Jason Earls, Aug 10 2005

			a(1)=2 because 12 = 1+3+4+6-2, the 2 is subtracted. a(6)=6 because 42 = 1+2+3+7+14+21-6, the 6 is subtracted.

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A033880, A111592, A111667.

a(n) = A033880(A111592(n))/2 = A111667(n)/2. - Amiram Eldar, Jun 22 2019

A109788 Admirable numbers whose abundance is < 10.

Original entry on oeis.org

12, 20, 56, 70, 88, 104, 368, 464, 650, 836, 1888, 1952, 4030, 5830, 8925, 11096, 17816, 32128, 32445, 45356, 77744, 91388, 128768, 130304, 254012, 388076, 442365, 521728, 522752, 1848964, 2087936, 2291936, 8378368, 8382464, 13174976, 29465852, 35021696, 45335936

Offset: 1

Jason Earls, Aug 14 2005

nonn

Apparently all the abundant numbers with even abundance < 10 are admirable (checked for the first 60 terms). Of the 4 known numbers whose abundance is 10 (A223609), only the first, 40, is admirable. - Amiram Eldar, Nov 07 2019

Amiram Eldar, Table of n, a(n) for n = 1..60

Cf. A033880, A111592, A111667.

aQ[n_] := (ab = DivisorSigma[1, n] - 2 n) > 0 && EvenQ[ab] && ab < 10 && ab/2 < n && Divisible[n, ab/2]; Select[Range[10^4], aQ] (* Amiram Eldar, Nov 07 2019 *)

for(n=1,10^9,my(ap=sigma(n)-2*n); if(ap>0 && ap<10 && ap%2==0, my(d=ap/2); if(d!=n && n%d==0, print1(n, ", ")))) \\ Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 30 2008

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 30 2008

a(36)-a(38) from Amiram Eldar, Nov 07 2019

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A111646 Subtracted divisor in admirable numbers.

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A109788 Admirable numbers whose abundance is < 10.

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