login
A064610
Places k where A064608(k) (partial sums of unitary tau) is divisible by k.
14
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
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 A279410 A061755
KEYWORD
nonn,more
AUTHOR
Labos Elemer, Sep 24 2001
EXTENSIONS
a(10)-a(13) from Donovan Johnson, Jul 20 2012
STATUS
approved