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%I A373971 #20 Jun 24 2024 10:50:33
%S A373971 0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,
%T A373971 0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,
%U A373971 0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
%N A373971 a(n) = 1 if n can be represented as a sum of 2 distinct positive cubes, otherwise 0.
%C A373971 Differs from A025468 first at n=1729, where a(1729) = 1, while A025468(1729) = 2.
%H A373971 Antti Karttunen, <a href="/A373971/b373971.txt">Table of n, a(n) for n = 0..100080</a>
%H A373971 <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%F A373971 a(n) = signum(A025468(n)) = [A025468(n) > 0], where [ ] is the Iverson bracket.
%F A373971 a(n) <= A373972(n).
%F A373971 a(n) <= A373973(n).
%e A373971 a(9) = 1 as 9 = 2^3 + 1^3.
%e A373971 a(35) = 1 as 35 = 3^3 + 2^3.
%o A373971 (PARI) A373971(n) = if(0==n,n,for(i=ceil(sqrtn(n\2+1, 3)), sqrtn(n-(1/2), 3), if(ispower(n-(i^3), 3), return(1))); 0); \\ After _M. F. Hasler_'s Apr 12 2008 program in A024670.
%Y A373971 Characteristic function of A024670.
%Y A373971 Cf. A010057, A025468, A373972, A373973, A373974 (inverse Möbius transform).
%K A373971 nonn
%O A373971 0
%A A373971 _Antti Karttunen_, Jun 24 2024

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