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A030142 Odd numbers in which parity of digits alternates. 6
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 (list; graph; refs; listen; history; text; internal format)
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: A083107 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

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Last modified February 21 14:40 EST 2018. Contains 299414 sequences. (Running on oeis4.)