A030157 Even numbers k such that in k^2 the parity of digits alternates.
0, 2, 4, 6, 16, 26, 36, 74, 84, 96, 204, 264, 296, 384, 404, 426, 574, 584, 606, 726, 736, 764, 874, 884, 964, 1464, 1584, 1596, 1704, 2036, 2074, 2084, 2184, 2916, 2926, 2964, 3306, 3536, 3764, 3816, 4116, 4264, 4306, 5684, 5726, 5736, 5874
Offset: 1
Links
- Giovanni Resta, Table of n, a(n) for n = 1..10000 (first 2000 terms from Robert Israel)
Crossrefs
Cf. A030158 (the squares).
Programs
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Maple
alp:= proc(n) local L,d; L:= convert(n,base,10); d:= nops(L); if d::even then L:= L + map(op, [[0,1]$(d/2)]) else L:= L + map(op, [[0,1]$((d-1)/2),[0]]) fi; nops(convert(L mod 2, set))=1 end proc: select(t -> alp(t^2), [seq(i,i=0..10000,2)]); # Robert Israel, Aug 15 2018
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Mathematica
id[n_]:=IntegerDigits[n^2]; t={}; Do[If[Length[id[n]]==1, AppendTo[t, n], If[Union[Abs[Differences[Boole/@EvenQ[id[n]]]]]=={1}, AppendTo[t, n]]], {n, 0, 6000, 2}]; t (* Vincenzo Librandi, Aug 15 2018 *) Join[{0,2},Select[Range[0,6000,2],Union[Abs[Differences[Boole[OddQ[ IntegerDigits[ #^2]]]]]] == {1}&]] (* Harvey P. Dale, Sep 11 2024 *)
Extensions
Offset changed by Robert Israel, Aug 15 2018