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!)
A334973 Odd bi-unitary admirable numbers: the odd terms of A334972. 2
945, 43065, 46035, 48195, 80535, 354585, 403095, 430815, 437745, 442365, 458055, 2305875, 3525795, 4404105, 4891887, 5388495, 5803245, 6126645, 6220665, 6375105, 6537375, 7853625, 7981875, 8109585, 8731125, 9071865, 9338595, 9784125, 13241745, 13351635, 23760555 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Of the first 10^4 bi-unitary admirable numbers only 11 are odd.

LINKS

Table of n, a(n) for n=1..31.

MATHEMATICA

fun[p_, e_] := If[OddQ[e], (p^(e + 1) - 1)/(p - 1), (p^(e + 1) - 1)/(p - 1) - p^(e/2)]; bsigma[1] = 1; bsigma[n_] := Times @@ (fun @@@ FactorInteger[n]); buDivQ[n_, 1] = True; buDivQ[n_, div_] := If[Mod[#2, #1] == 0, Last@Apply[Intersection, Map[Select[Divisors[#], Function[d, CoprimeQ[d, #/d]]] &, {#1, #2/#1}]] == 1, False] & @@ {div, n}; buAdmQ[n_] := (ab = bsigma[n] - 2 n) > 0 && EvenQ[ab] && ab/2 < n && Divisible[n, ab/2] && buDivQ[n, ab/2]; Select[Range[1, 5*10^5, 2], buAdmQ]

CROSSREFS

The bi-unitary version of A109729.

Intersection of A005408 and A334972.

Subsequence of A293186.

Cf. A329188, A334975.

Sequence in context: A290034 A335055 A133818 * A334975 A289953 A112491

Adjacent sequences:  A334970 A334971 A334972 * A334974 A334975 A334976

KEYWORD

nonn

AUTHOR

Amiram Eldar, May 18 2020

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 July 26 01:33 EDT 2021. Contains 346294 sequences. (Running on oeis4.)