login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A046681 Number of divisors of n and sum of 4th powers of divisors of n are relatively prime. 7
1, 2, 8, 9, 18, 64, 72, 128, 625, 729, 1024, 1152, 1250, 1458, 4096, 5000, 5625, 5832, 6561, 8192, 9216, 11250, 13122, 15625, 31250, 32768, 40000, 45000, 46656, 52488, 59049, 65536, 80000, 93312, 117649, 118098, 125000, 235298, 262144, 294912 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

It can be shown that this is a subset of A028982.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..5000

MATHEMATICA

Select[Range[300000], CoprimeQ[DivisorSigma[0, #], DivisorSigma[4, #]]&] (* Harvey P. Dale, May 30 2012 *)

PROG

(PARI) isok(n) = gcd(sigma(n, 4), numdiv(n)) == 1; \\ Michel Marcus, Sep 24 2019

CROSSREFS

Cf. A028982, A046678, A046679, A046680, A046683, A046685.

Sequence in context: A118962 A096033 A073413 * A259672 A163619 A166968

Adjacent sequences:  A046678 A046679 A046680 * A046682 A046683 A046684

KEYWORD

nonn

AUTHOR

Labos Elemer

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 November 21 14:18 EST 2019. Contains 329371 sequences. (Running on oeis4.)