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Integers k which equal (product of divisors of k) mod (sum of divisors of k).
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%I #18 Jun 27 2024 22:15:50

%S 2,3,5,7,10,11,13,17,19,20,23,29,31,33,37,40,41,43,47,53,59,61,67,71,

%T 73,76,79,83,89,97,101,103,107,109,113,127,131,136,137,139,145,149,

%U 151,157,163,167,173,179,181,191,193,197,199,207,211,223,227,229,233,239,241,251,257,261,263,269,271,277

%N Integers k which equal (product of divisors of k) mod (sum of divisors of k).

%H G. C. Greubel, <a href="/A187711/b187711.txt">Table of n, a(n) for n = 1..10000</a>

%F { k : k = A187680(k) }.

%p isA187711 := proc(n) is(A187680(n) = n) end proc:

%p for n from 2 to 300 do if isA187711(n) then printf("%d,",n) ; end if; end do: # _R. J. Mathar_, Mar 17 2011

%t Select[Range[300], Mod[#^(DivisorSigma[0, #]/2), DivisorSigma[1, #]] == # &] (* _G. C. Greubel_, Nov 05 2018 *)

%Y Cf. A000203, A007955, A187680.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Mar 17 2011