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Numbers that have exactly one Zumkeller divisor.
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%I #24 Oct 27 2024 11:47:03

%S 6,18,20,28,70,88,100,104,196,272,304,368,464,496,550,572,650,836,945,

%T 968,1184,1312,1352,1376,1430,1504,1575,1696,1870,1888,1952,2002,2090,

%U 2205,2210,2470,2530,2584,2990,3128,3190,3230,3410,3465,3496,3770,3944

%N Numbers that have exactly one Zumkeller divisor.

%C d is a Zumkeller divisor of n if and only if d is a divisor of n and is Zumkeller (A083207).

%H Michael S. Branicky, <a href="/A376881/b376881.txt">Table of n, a(n) for n = 1..10000</a>

%F If d is the only Zumkeller divisor of n and n is Zumkeller then d = n.

%p # The function 'isZumkeller' is defined in A376880.

%p zdiv := n -> select(isZumkeller, NumberTheory:-Divisors(n)):

%p select(n -> nops(zdiv(n)) = 1, [seq(1..4000)]);

%Y Subsequence of A376880.

%Y Cf. A083207, A376877, A376882, A023196, A171641.

%K nonn

%O 1,1

%A _Peter Luschny_, Oct 19 2024