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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A109396 Admirable Harshad numbers such that the subtracted divisor is also a Harshad number. 1
12, 20, 24, 30, 40, 42, 54, 70, 102, 114, 120, 222, 270, 402, 1002, 2022, 2202, 10002, 10014, 10792, 11202, 12102, 21102, 31002, 32128, 45356, 103002, 110202, 111102, 128768, 740870, 1000002, 1000014, 1001202, 1002102, 1021002, 1111002, 1200102 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..100

EXAMPLE

12 is in the sequence since it is a Harshad number (1 + 2 = 3 is a divisor of 12), an admirable number: 1 - 2 + 3 + 4 + 6 = 12, and the subtracted divisor, 2, is also a Harshad number.

MATHEMATICA

hQ[n_] := Divisible[n, Plus @@ IntegerDigits@n]; aQ[n_] := hQ[n] && (d = DivisorSigma[1, n] - 2*n) > 0 && EvenQ[d] && d/2 < n && hQ[d/2] && Divisible[n, d/2]; Select[Range[50000], aQ] (* Amiram Eldar, Oct 27 2019 *)

CROSSREFS

Cf. A111592, A005349, A111947, A111948.

Sequence in context: A204825 A111592 A111947 * A286004 A055598 A302297

Adjacent sequences:  A109393 A109394 A109395 * A109397 A109398 A109399

KEYWORD

base,nonn

AUTHOR

Jason Earls, Aug 26 2005

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 April 10 10:39 EDT 2021. Contains 342845 sequences. (Running on oeis4.)