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 A074993 a(n) = floor((concatenation of n, n+1)/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, 1818, 1869, 1919, 1970, 2020, 2071, 2121, 2172, 2222, 2273, 2323, 2374 (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 MATHEMATICA cc[n_]:=Floor[FromDigits[Join[IntegerDigits[n], IntegerDigits[n+1]]]/2]; Array[cc, 40, 0] (* Harvey P. Dale, Nov 11 2011 *) CROSSREFS Cf. A001704, A074991, A074992, A074994, A074995, A074996, A074997, A073086, A074999, A127421. 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 June 19 14:40 EDT 2021. Contains 345140 sequences. (Running on oeis4.)