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A227429
Numbers k such that Sum_{j=1..k} j^phi(j) == 0 (mod k).
8
1, 3, 4, 12, 21, 39, 91, 156, 381, 1668, 3292, 4541, 6515, 12927, 49492, 72412, 100595, 158708
OFFSET
1,2
COMMENTS
a(17) > 10^5. - Giovanni Resta, Jul 11 2013
a(19) > 2473000. - Kevin P. Thompson, Nov 28 2021
EXAMPLE
4 is a member of the sequence since Sum_{j=1..4} j^phi(j) = 1^phi(1) + 2^phi(2) + 3^phi(3) + 4^phi(4) = 1^1 + 2^1 + 3^2 + 4^2 = 28 which is divisible by 4.
MAPLE
with(numtheory); ListA227429:=proc(q) local i, n;
for n from 1 to q do if add(i^phi(i), i=1..n) mod n=0 then print(n);
fi; od; end: ListA227429(10^6);
CROSSREFS
Sequence in context: A281892 A101727 A292551 * A075220 A075221 A295948
KEYWORD
nonn,more
AUTHOR
Paolo P. Lava, Jul 11 2013
EXTENSIONS
a(10)-a(16) from Giovanni Resta, Jul 11 2013
a(17)-a(18) from Kevin P. Thompson, Nov 28 2021
STATUS
approved