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Put the natural numbers together without spaces and read them two at a time advancing one space each time.
6

%I #18 Mar 26 2014 02:11:38

%S 12,23,34,45,56,67,78,89,91,10,1,11,11,12,21,13,31,14,41,15,51,16,61,

%T 17,71,18,81,19,92,20,2,21,12,22,22,23,32,24,42,25,52,26,62,27,72,28,

%U 82,29,93,30,3,31,13,32,23,33,33,34,43,35,53,36,63,37,73,38,83,39,94,40,4,41,14

%N Put the natural numbers together without spaces and read them two at a time advancing one space each time.

%C a(n) = A162711(n,2) for n>1. - _Reinhard Zumkeller_, Jul 11 2009

%H Reinhard Zumkeller, <a href="/A136414/b136414.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = 10*A007376(n) + A007376(n+1). - _Reinhard Zumkeller_, Jul 11 2009

%e 34 is the third entry because the natural numbers written together look like 1234567891011 and reading them off two at a time produces 12, 23, 34, ...

%o (Haskell)

%o a136414 n = a136414_list !! (n-1)

%o a136414_list = zipWith (+) (tail a007376_list) $ map (10 *) a007376_list

%o -- _Reinhard Zumkeller_, Jul 28 2011

%Y Cf. A001704, A193431, A193492, A193493.

%K easy,nonn,base,look

%O 1,1

%A _Ben Paul Thurston_, Mar 31 2008

%E More terms from _Reinhard Zumkeller_, Jul 11 2009