cp's OEIS Frontend

A367084 Indices k such that A367083(k) and A367083(k+1) are both odd.

%I A367084 #10 Nov 09 2023 10:51:50
%S A367084 0,7,16,25,34,43,50,59,68,77,86,95,102,111,120,129,138,145,154,163,
%T A367084 172,181,190,197,206,215,224,233,240,249,258,267,276,285,292,301,310,
%U A367084 319,328,335,344,353,362,371,380,387,396,405,414,423,430,439,448,457,466,475,482,491,500
%N A367084 Indices k such that A367083(k) and A367083(k+1) are both odd.
%C A367084 First differences are either 7 (in isolated positions) or 9 (always 4 or 5 times consecutively in a row). It is interesting to study these run lengths, see A367083 for further information.
%o A367084 (PARI) A367084_upto(N) = [n|n<-A=A367083_upto(N), A[n+1]==Mod(A[n],2)]
%o A367084 (Python)
%o A367084 from itertools import islice
%o A367084 def A367084_gen(): # generator of terms
%o A367084     a, b, c = 1, 4, -1
%o A367084     while True:
%o A367084         while (a:=a*3)<b:
%o A367084             yield (c:=c+1)
%o A367084         b <<= 2
%o A367084         c += 2
%o A367084 A367084_list = list(islice(A367084_gen(),30)) # _Chai Wah Wu_, Nov 08 2023
%Y A367084 Cf. A367083, A327621.
%K A367084 nonn
%O A367084 0,2
%A A367084 _M. F. Hasler_, Nov 03 2023