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A229095 Numbers n such that sum_{i=1..n} i^tau(i) == 0 (mod n), where tau(i) = A000005(i), the number of divisors of i. 6
1, 8, 9, 67, 72, 467, 801, 1071, 5141, 7193, 25688, 68488, 97768, 111816, 381061 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..15.

EXAMPLE

1^tau(1) + 2^tau(2) + … + 8^tau(8) + 9^tau(9) = 1^1 + 2^2 + 3^2 + 4^3 + 5^2 + 6^4 + 7^2 + 8^4 + 9^3 = 6273 and 6273 / 9 = 697.

MAPLE

with(numtheory); P:=proc(q) local n, t; t:=0;

for n from 1 to q do t:=t+n^tau(n); if t mod n=0 then print(n);

fi; od; end: P(10^6);

CROSSREFS

Cf. A000005, A227427, A227429, A227502, A227848.

Sequence in context: A025633 A249697 A038287 * A041140 A195940 A195991

Adjacent sequences:  A229092 A229093 A229094 * A229096 A229097 A229098

KEYWORD

nonn

AUTHOR

Paolo P. Lava, Sep 13 2013

STATUS

approved

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Last modified October 18 23:39 EDT 2019. Contains 328211 sequences. (Running on oeis4.)