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

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, 119, 127, 137, 181, 187, 204, 237, 264, 269, 273, 277, 281, 296, 311, 384, 404, 426, 461, 463, 539, 574, 584, 606, 661, 673, 677, 689, 726, 736, 764, 819

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Links

• Giovanni Resta, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A030152, A030153, A030154, A030159.

Programs

Mathematica

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 *)