A030142 Odd numbers in which parity of digits alternates.

1, 3, 5, 7, 9, 21, 23, 25, 27, 29, 41, 43, 45, 47, 49, 61, 63, 65, 67, 69, 81, 83, 85, 87, 89, 101, 103, 105, 107, 109, 121, 123, 125, 127, 129, 141, 143, 145, 147, 149, 161, 163, 165, 167, 169, 181, 183, 185, 187, 189, 301, 303, 305, 307, 309, 321, 323

Offset

1,2

Comments

a(n) = A179085(n) for n <= 25. - Reinhard Zumkeller, Jun 28 2010

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Index entries for 10-automatic sequences.

Formula

(a(n) mod 2) * A228710(a(n)) = 1. - Reinhard Zumkeller, Aug 31 2013

Mathematica

id[n_]:=IntegerDigits[n]; t={}; Do[If[Length[id[n]]==1, AppendTo[t, n], If[Union[Abs[Differences[Boole /@ EvenQ[id[n]]]]] == {1}, AppendTo[t, n]]], {n, 1, 323, 2}]; t (* Jayanta Basu, May 07 2013 *)
Join[{1, 3, 5, 7, 9}, Select[Range[21, 323, 2], Total[Abs[Differences[Mod[(id = IntegerDigits[#]), 2]]]] == Length[id] - 1 &]] (* Zak Seidov, May 07 2013 *)

Prog

(Haskell)
a030142 n = a030142_list !! (n-1)
a030142_list = filter odd a030141_list
-- Reinhard Zumkeller, Aug 31 2013

Crossrefs

Cf. A030143, A062285, intersection of A005408 and A030141.

Sequence in context: A338637 A003052 A003219 * A179085 A076185 A101813

Adjacent sequences: A030139 A030140 A030141 * A030143 A030144 A030145

Keyword

nonn,base,easy

Author

Patrick De Geest

Extensions

Offset corrected by Reinhard Zumkeller, Jun 28 2010

Status

approved