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%I #11 Aug 22 2021 22:38:13
%S 0,1,0,0,1,1,1,1,0,0,1,0,0,1,0,0,0,1,1,1,1,0,0,1,0,1,0,1,0,0,1,0,0,0,
%T 0,1,0,1,1,0,0,1,0,0,1,1,1,0,0,0,1,1,0,0,0,1,0,0,1,0,1,1,1,0,1,0,0,1,
%U 1,1,1,1,1,1,1,1,1,1,1,1,0,0,1,0,1,1,1,0,1,0,0,1,0,0,1,0,0,0,1,1,0,0,0,1,0,0
%N Sequence A071673 reduced modulo 2.
%H Antti Karttunen, <a href="/A071674/b071674.txt">Table of n, a(n) for n = 0..10440 (rows 0..144 of the triangle, flattened)</a>
%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%F a(n) = A000035(A071673(n)).
%e The first 15 rows of this irregular triangular table:
%e 0,
%e 1,
%e 0, 0,
%e 1, 1, 1,
%e 1, 0, 0, 1,
%e 0, 0, 1, 0, 0,
%e 0, 1, 1, 1, 1, 0,
%e 0, 1, 0, 1, 0, 1, 0,
%e 0, 1, 0, 0, 0, 0, 1, 0,
%e 1, 1, 0, 0, 1, 0, 0, 1, 1,
%e 1, 0, 0, 0, 1, 1, 0, 0, 0, 1,
%e 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0,
%e 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
%e 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 1,
%e 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0,
%e etc.
%o (PARI)
%o up_to = 10440;
%o A002260(n) = (n-binomial((sqrtint(8*n)+1)\2, 2)); \\ From A002260
%o A004736(n) = (1-n+(n=sqrtint(8*n)\/2)*(n+1)\2); \\ From A004736
%o A071673list(up_to) = { my(v=vector(1+up_to)); v[1] = 0; for(n=1,up_to,v[1+n] = 1 + v[A004736(n)] + v[A002260(n)]); (v); };
%o v071673 = A071673list(up_to);
%o A071673(n) = v071673[1+n];
%o A071674(n) = (A071673(n)%2); \\ _Antti Karttunen_, Aug 22 2021
%Y Cf. A000035, A071673.
%K nonn,tabf
%O 0
%A _Antti Karttunen_, May 30 2002
%E Term a(0) = 0 prepended and the Example section added by _Antti Karttunen_, Aug 22 2021
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