A184989 Digits of n and of n-1 interleaved in decimal representation.

10, 21, 32, 43, 54, 65, 76, 87, 98, 190, 1110, 1121, 1132, 1143, 1154, 1165, 1176, 1187, 1198, 2109, 2210, 2221, 2232, 2243, 2254, 2265, 2276, 2287, 2298, 3209, 3310, 3321, 3332, 3343, 3354, 3365, 3376, 3387, 3398, 4309, 4410, 4421, 4432, 4443, 4454, 4465, 4476, 4487, 4498, 5409, 5510, 5521, 5532, 5543, 5554, 5565, 5576, 5587, 5598

Offset

1,1

Comments

A055642(a(n)) <= 2*A055642(n), equality holds iff n <> 10^k;

A007953(a(n)) = 2*A007953(n) - 1 + 9*A122840(n);

1, 10, 2207, 7877, 9829, 2240353, 6682447, ... are the first numbers m such that a(m) is a multiple of m.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..9999

Mathematica

Table[FromDigits[Riffle[IntegerDigits[n], IntegerDigits[n-1]]], {n, 60}] (* Harvey P. Dale, Aug 11 2015 *)

Prog

(Haskell)
a184989 n = read $ interleave (show n) (show (n - 1)) :: Integer where
   interleave []     ys = ys
   interleave (x:xs) ys = x : interleave ys xs

Crossrefs

Sequence in context: A095778 A065438 A017509 * A072806 A189402 A051942

Adjacent sequences: A184986 A184987 A184988 * A184990 A184991 A184992

Keyword

nonn,base,look

Author

Reinhard Zumkeller, Mar 29 2011

Status

approved