A324543 - OEIS

A324543

Möbius transform of A323243, where A323243(n) = sigma(A156552(n)).

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

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OFFSET

1,3

COMMENTS

The first four zeros after a(1) occur at n = 192, 288, 3645, 6075.

There are 1562 negative terms among the first 10000 terms.

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

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A324201 divisors a(n) applied to each: Sum

9: [1, 3, 9] -> [0, 3, 9] 12 = 2*6

125: [1, 5, 25, 125] -> [0, 7, 21, 28] 56 = 2*28

161051: [1, 11, 121, 1331, 14641, 161051] -> [0, 31, 93, 124, 496, 248] 992 = 2*496

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

-> [0, 127, 381, 508, 2032, 1016, 9144, 3048] 16256 = 2*8128

The second term (the first nonzero) of the latter list = A000668(n), and the sum is always twice the corresponding 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 A367034

Adjacent sequences: A324540 A324541 A324542 * A324544 A324545 A324546

KEYWORD

sign,changed

AUTHOR

Antti Karttunen, Mar 07 2019

STATUS

approved