A001704 a(n) = n concatenated with n + 1.
12, 23, 34, 45, 56, 67, 78, 89, 910, 1011, 1112, 1213, 1314, 1415, 1516, 1617, 1718, 1819, 1920, 2021, 2122, 2223, 2324, 2425, 2526, 2627, 2728, 2829, 2930, 3031, 3132, 3233, 3334, 3435, 3536, 3637, 3738, 3839, 3940, 4041, 4142, 4243, 4344, 4445, 4546
Offset: 1
Links
- N. J. A. Sloane, Table of n, a(n) for n = 1..25000 (first 1000 terms from T. D. Noe)
Programs
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Haskell
a001704 n = a001704_list !! (n-1) a001704_list = map read (zipWith (++) iss $ tail iss) :: [Integer] where iss = map show [1..] -- Reinhard Zumkeller, Oct 07 2014 -
Magma
[Seqint(Intseq(n+1) cat Intseq(n)): n in [1..50]]; // Vincenzo Librandi, Jul 08 2018
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Maple
f:=proc(i) i*10^(1+floor(evalf(log10(i+1), 10)))+i+1; end: # gives a(n) - N. J. A. Sloane, Aug 04 2012 # alternative Maple program: a:= n-> parse(cat(n, n+1)): seq(a(n), n=1..55); # Alois P. Heinz, Jul 05 2018
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Mathematica
Table[FromDigits@Flatten@IntegerDigits[{n, n + 1}], {n, 100}] (* T. D. Noe, Aug 09 2012 *) -
PARI
a(n)=eval(Str(n,n+1)) \\ Charles R Greathouse IV, Jul 23 2016 (Emacs Lisp) ;; Concatenation (defun A001704 (n) (string-to-int (concat (int-to-string n) (int-to-string (1+ n))))) ;; Formula (defun A001704 (n) (1+ n (* n (expt 10 (1+ (floor (log (1+ n) 10))))))) (mapcar '(lambda (n) (cons n (A001704 n))) '(1 2 3 10 11 12 99 999)) => ((1 . 12) (2 . 23) (3 . 34) (10 . 1011) (11 . 1112) (12 . 1213) (99 . 99100) (999 . 9991000)) ; Tim Chambers, Jul 07 2018
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Python
for n in range(1,100): print(str(n)+str(n+1)) # David F. Marrs, Sep 17 2018
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Scala
val numerStrs = (1 to 50).map(Integer.toString(_)).toList val concats = (numerStrs.dropRight(1)) zip (numerStrs.drop(1)) concats.map(x => Integer.parseInt(x.1 + x._2)) // _Alonso del Arte, Oct 24 2019
Extensions
More terms from Joshua Zucker and Jon E. Schoenfield, May 15 2007
Comments