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A074993 Floor[concatenation of n, n+1 divided by 2]. 9
0, 6, 11, 17, 22, 28, 33, 39, 44, 455, 505, 556, 606, 657, 707, 758, 808, 859, 909, 960, 1010, 1061, 1111, 1162, 1212, 1263, 1313, 1364, 1414, 1465, 1515, 1566, 1616, 1667, 1717, 1768 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

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.

LINKS

Table of n, a(n) for n=0..35.

MATHEMATICA

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

CROSSREFS

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

Sequence in context: A315522 A315523 A315524 * A315525 A231001 A315526

Adjacent sequences:  A074990 A074991 A074992 * A074994 A074995 A074996

KEYWORD

base,easy,nonn

AUTHOR

Amarnath Murthy, Aug 31 2002

STATUS

approved

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Last modified October 21 13:57 EDT 2019. Contains 328299 sequences. (Running on oeis4.)