A348586 Numbers k such that abs(A328258(k)) = abs(A328258(k+1)).

1, 11, 40, 179, 695, 928, 991, 1079, 2772, 2799, 2839, 6687, 7632, 7739, 7960, 8568, 9347, 10703, 11008, 11472, 12847, 12935, 13580, 14064, 16000, 16260, 17135, 20944, 26432, 27999, 35399, 37236, 42251, 42756, 44199, 55308, 56419, 68976, 70127, 74671, 77748, 83099

Offset

1,2

Comments

Equivalently, numbers k such that A328258(k) = -A328258(k+1).

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Example

1 is a term since abs(A328258(1)) = abs(A328258(2)) = 1.
11 is a term since abs(A328258(11)) = abs(A328258(12)) = 12.

Mathematica

f[p_, e_] := 1 - (-1)^p*(p^e); s[1] = 1; s[n_] := Abs[Times @@ (f @@@ FactorInteger[n])]; Select[Range[10^5], s[#] == s[# + 1] &]

Prog

(PARI) f(n) = sumdiv(n, d, if (gcd(d, n/d) == 1, (-1)^(d + 1) * d)); \\ A328258
isok(k) = f(k) + f(k+1) == 0; \\ Michel Marcus, Oct 24 2021

Crossrefs

The unitary version of A348585.

Cf. A328258.

Similar sequences: A002961, A064125, A206368, A333261.

Sequence in context: A056124 A356043 A225919 * A064768 A135719 A089776

Adjacent sequences: A348583 A348584 A348585 * A348587 A348588 A348589

Keyword

nonn

Author

Amiram Eldar, Oct 24 2021

Status

approved