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!)
A318781 A188999(m)/m for the integers m such that A188999(m) is divisible by m, where A188999 is the bi-unitary sigma function. 1
1, 2, 2, 2, 3, 3, 3, 3, 3, 4, 3, 3, 4, 3, 4, 3, 4, 3, 3, 4, 4, 3, 3, 3, 4, 4, 4, 3, 3, 4, 3, 4, 4, 3, 4, 3, 3, 4, 4, 4, 4, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

10496266260480 is a term of A189000 and it is the smallest known value x such that A188999(x)/x is 5.

LINKS

Table of n, a(n) for n=1..42.

FORMULA

a(n) = A188999(A189000(n))/A189000(n).

PROG

(PARI) a188999(n) = my(f = factor(n)); for (i=1, #f~, p = f[i, 1]; e = f[i, 2]; f[i, 1] = if (e % 2, (p^(e+1)-1)/(p-1), (p^(e+1)-1)/(p-1) -p^(e/2)); f[i, 2] = 1; ); factorback(f) \\ after Michel Marcus in A189000

is_a189000(n) = ! frac(a188999(n)/n) \\ after Michel Marcus in A189000

for(n=1, oo, if(is_a189000(n), print1(a188999(n)/n, ", "))) \\ Felix Fröhlich, Sep 03 2018

CROSSREFS

Cf. A188999 (bi-unitary sigma), A189000 (multiply perfect for bi-unitary sigma).

Cf. A054030 (analog for sigma), A007691 (multiply perfect for sigma).

Sequence in context: A074795 A069577 A282426 * A316844 A331245 A130239

Adjacent sequences:  A318778 A318779 A318780 * A318782 A318783 A318784

KEYWORD

nonn,more

AUTHOR

Michel Marcus, Sep 03 2018, following a suggestion from Felix Fröhlich

EXTENSIONS

a(33)-a(42) from Giovanni Resta, Sep 03 2018

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 24 06:04 EDT 2021. Contains 346273 sequences. (Running on oeis4.)