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 A030151 Numbers k such that in k^2 the parity of digits alternates. 7

%I

%S 0,1,2,3,4,5,6,7,9,11,13,16,19,23,26,27,31,36,69,74,81,84,96,111,113,

%T 119,127,137,181,187,204,237,264,269,273,277,281,296,311,384,404,426,

%U 461,463,539,574,584,606,661,673,677,689,726,736,764,819

%N Numbers k such that in k^2 the parity of digits alternates.

%H Giovanni Resta, <a href="/A030151/b030151.txt">Table of n, a(n) for n = 1..10000</a>

%t upto=2000;tfs=Flatten[Table[{True,False},{Ceiling[IntegerLength[ upto]]}]]; altparQ[n_]:= Module[{n2=n^2},MemberQ[Partition[ tfs,IntegerLength[n2],1], EvenQ/@IntegerDigits[n2]]]; Join[{0},Select[Range[upto],altparQ]] (* _Harvey P. Dale_, May 12 2011 *)

%Y Cf. A030152, A030153, A030154, A030159.

%K nonn,base

%O 1,3

%A _Patrick De Geest_

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Last modified December 7 17:25 EST 2022. Contains 358668 sequences. (Running on oeis4.)