A064610 Places k where A064608(k) (partial sums of unitary tau) is divisible by k.

1, 35, 37, 1015, 27417, 27421, 27449, 27453, 19774739, 530743781, 530743799, 530743807, 530743813

Offset

1,2

Comments

The corresponding quotients are 1, 3, 3, 5, 7, 7, 7, 7, 11, 13, 13, 13, 13, ...

a(14) > 7.5*10^10, if it exists. - Amiram Eldar, Jun 04 2021

Links

Table of n, a(n) for n=1..13.

Formula

{n: A064608(n) == 0 (mod n)}.

Example

For n = 37, the sum A064608(37) = 1+2+2+2+2+4+2+...+4+4+4+2 = 111 = 3*37, so 37 is in the sequence.

Mathematica

s[1] = 1; s[n_] := s[n] = s[n - 1] + 2^PrimeNu[n]; Select[Range[30000], Divisible[s[#], #] &] (* Amiram Eldar, Jun 04 2021 *)

Crossrefs

Cf. A064608.

Analogous "integer-mean" sequences for various arithmetical functions are A050226, A056650, A064605, A064606, A064607, A048290, A063986, A063971, A064911, A062982, A045345.

Sequence in context: A160775 A160021 A172016 * A030589 A114965 A279410

Adjacent sequences: A064607 A064608 A064609 * A064611 A064612 A064613

Keyword

nonn,more

Author

Labos Elemer, Sep 24 2001

Extensions

a(10)-a(13) from Donovan Johnson, Jul 20 2012

Status

approved