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!)
A324543 Möbius transform of A323243, where A323243(n) = sigma(A156552(n)). 15
0, 1, 3, 3, 7, 2, 15, 4, 9, 5, 31, 3, 63, 2, 8, 16, 127, -1, 255, 4, 21, 16, 511, 8, 21, 20, 12, 27, 1023, 6, 2047, 8, 20, 48, 20, 20, 4095, 2, 78, 32, 8191, -6, 16383, 17, 9, 288, 32767, 8, 45, -3, 122, 45, 65535, 4, 53, 20, 270, 278, 131071, 2, 262143, 688, 12, 72, 56, 23, 524287, 125, 260, -8, 1048575, 20, 2097151, 260, 3, 363, 44, -7, 4194303 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

The first three zeros after a(1) occur at n = 192, 288, 3645.

There are 630 negative terms among the first 4473 terms.

Applying this function to the divisors of the first four terms of A324201 reveals the following pattern:

----------------------------------------------------------------------------------

A324201(n) divisors                             a(n) applied to each:         Sum

        9: [1, 3, 9]                         -> [0, 3, 9]                      12

      125: [1, 5, 25, 125]                   -> [0, 7, 21, 28]                 56

   161051: [1, 11, 121, 1331, 14641, 161051] -> [0, 31, 93, 124, 496, 248]    496

410338673: [1, 17, 289, 4913, 83521, 1419857, 24137569, 410338673]

                             -> [0, 127, 381, 508, 2032, 1016, 9144, 3048]  16256.

The second term (the first nonzero) of the latter list = A000668(n), and the sum is always twice the corresponding (even) perfect number, which forces either it or at least many of its divisors to be present. For example, in the fourth case, although 8128 = A000396(4) itself is not present, we still have 127, 508, 1016 and 2032 in the list. See also A329644.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000 (based on Hans Havermann's factorization of A156552)

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to sigma(n)

FORMULA

a(n) = Sum_{d|n} A008683(n/d) * A323243(d).

a(A000040(n)) = A000225(n).

a(A001248(n)) = A173033(n) - A000225(n) = A068156(n) = 3*(2^n - 1).

a(2*A000040(n)) = A324549(n).

a(A002110(n)) = A324547(n).

a(n) = 2*A297112(n) - A329644(n), and for n > 1, a(n) = 2^A297113(n) - A329644(n). - Antti Karttunen, Dec 08 2019

MATHEMATICA

Table[DivisorSum[n, MoebiusMu[n/#] If[# == 1, 0, DivisorSigma[1, Floor@ Total@ Flatten@ MapIndexed[#1 2^(#2 - 1) &, Flatten[Table[2^(PrimePi@ #1 - 1), {#2}] & @@@ FactorInteger@ #]]]] &], {n, 79}] (* Michael De Vlieger, Mar 11 2019 *)

PROG

(PARI)

A064989(n) = {my(f); f = factor(n); if((n>1 && f[1, 1]==2), f[1, 2] = 0); for (i=1, #f~, f[i, 1] = precprime(f[i, 1]-1)); factorback(f)};

A156552(n) = if(1==n, 0, if(!(n%2), 1+(2*A156552(n/2)), 2*A156552(A064989(n))));

memoA323243 = Map();

A323243(n) = if(1==n, 0, my(v); if(mapisdefined(memoA323243, n, &v), v, v=sigma(A156552(n)); mapput(memoA323243, n, v); (v)));

A324543(n) = sumdiv(n, d, moebius(n/d)*A323243(d));

CROSSREFS

Cf. A000040, A000043, A000668, A000203, A000225, A000396, A008683, A068156, A156552, A173033, A297112, A297113, A323243, A323244, A324201, A324542, A324547, A324548, A324549, A324712, A329644.

Sequence in context: A280753 A076217 A256784 * A333339 A089488 A076560

Adjacent sequences:  A324540 A324541 A324542 * A324544 A324545 A324546

KEYWORD

sign

AUTHOR

Antti Karttunen, Mar 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 15 16:11 EST 2021. Contains 340187 sequences. (Running on oeis4.)