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A074993 Floor[concatenation of n, n+1 divided by 2]. 9

%I

%S 0,6,11,17,22,28,33,39,44,455,505,556,606,657,707,758,808,859,909,960,

%T 1010,1061,1111,1162,1212,1263,1313,1364,1414,1465,1515,1566,1616,

%U 1667,1717,1768

%N Floor[concatenation of n, n+1 divided by 2].

%C The first differences follow a pattern. Odd indexed terms and even indexed terms form separate A.P.s with the same common difference for all n except n = 10^k -1. The corresponding common differences are the repunits = {10^(d+1)-1}/9 where d = the number of digits in n.

%t cc[n_]:=Floor[FromDigits[Join[IntegerDigits[n],IntegerDigits[n+1]]]/2]; Array[cc,40,0] (* _Harvey P. Dale_, Nov 11 2011 *)

%Y Cf. A074991, A074992, A074994, A074995, A074996, A074997, A073086, A074999.

%K base,easy,nonn

%O 0,2

%A _Amarnath Murthy_, Aug 31 2002

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Last modified November 18 14:37 EST 2019. Contains 329262 sequences. (Running on oeis4.)