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

1,2

Links

Giovanni Resta, Table of n, a(n) for n = 1..10000 (first 2000 terms from Robert Israel)

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

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 *)

Crossrefs

Cf. A030158 (the squares).

Sequence in context: A228119 A078148 A076075 * A162580 A098426 A365639

Adjacent sequences: A030154 A030155 A030156 * A030158 A030159 A030160

Keyword

nonn,base

Author

Patrick De Geest

Extensions

Offset changed by Robert Israel, Aug 15 2018

Status

approved