login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A109788 Admirable numbers such that their abundance is < 10. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Apparently all the abundant numbers with even abundance < 10 are admirable (checked on 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

LINKS

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

MATHEMATICA

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 *)

PROG

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

CROSSREFS

Cf. A033880, A111592, A111667.

Sequence in context: A063690 A229355 A259174 * A181701 A025104 A163323

Adjacent sequences:  A109785 A109786 A109787 * A109789 A109790 A109791

KEYWORD

nonn

AUTHOR

Jason Earls, Aug 14 2005

EXTENSIONS

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

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

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 23 04:16 EST 2020. Contains 331168 sequences. (Running on oeis4.)