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%I #18 Aug 07 2023 02:12:59
%S 1,1,5,1,3,1,1,1,5,1,1,1,3,1,5,1,3,1,1,1,3,1,5,1,1,1,5,1,3,1,1,1,5,1,
%T 1,1,3,1,5,1,1,1,5,1,3,1,1,1,3,1,5,1,3,1,1,1,5,1,1,1,3,1,5,1,3,1,1,1,
%U 3,1,5,1,1,1,5,1,3,1,1,1,3,1,5,1,3,1,1,1,5,1,1,1,3,1,5,1,1
%N Run lengths of A228495 (Characteristic function of the odd odious numbers).
%C Also run lengths of A254377 = 1-A228495(n).
%H Antti Karttunen, <a href="/A254378/b254378.txt">Table of n, a(n) for n = 1..65537</a>
%e A228495 begins 0,1,0,0,0,0,0,1,0, hence this sequence begins 1,1,5,1.
%t Length /@ Split[Table[If[OddQ[n] && OddQ[DigitCount[n, 2, 1]], 1, 0], {n, 0, 200}]] (* _Amiram Eldar_, Aug 07 2023 *)
%o (PARI)
%o up_to = 65537;
%o A254378lista(up_to) = { my(v=vector(up_to), r=1, n=0, i=1, pb=0, b); while(n<up_to, b = (hammingweight(i)%2)*(i%2); if(b==pb, r++, n++; v[n] = r; r = 1; pb = b); i++); (v); }; \\ _Antti Karttunen_, Oct 01 2018
%o v254378 = A254378lista(up_to);
%o A254378(n) = v254378[n]; \\ _Antti Karttunen_, Oct 01 2018
%o (Python)
%o from itertools import count, islice, groupby
%o def A254378_gen(): # generator of terms
%o return (len(list(g)) for k, g in groupby(n.bit_count()&1&n for n in count(0)))
%o A254378_list = list(islice(A254378_gen(),20)) # _Chai Wah Wu_, Mar 09 2023
%Y Cf. A228495, A254377, A254655.
%K nonn,base
%O 1,3
%A _Jeremy Gardiner_, Jan 29 2015
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