A193431 - OEIS

%I #16 Nov 16 2021 16:53:24

%S 123,234,345,456,567,678,789,891,910,101,11,111,112,121,213,131,314,

%T 141,415,151,516,161,617,171,718,181,819,192,920,202,21,212,122,222,

%U 223,232,324,242,425,252,526,262,627,272,728,282,829,293,930,303,31,313

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

%H Reinhard Zumkeller, <a href="/A193431/b193431.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = 10 * (10 * A007376(n) + A007376(n+1)) + A007376(n+2).

%t Module[{nn=50,d},d=Flatten[IntegerDigits/@Range[nn]];FromDigits/@ Partition[ d,3,1]] (* _Harvey P. Dale_, Nov 16 2021 *)

%o (Haskell)

%o a193431 n = a193431_list !! (n-1)

%o a193431_list = f a007376_list where

%o    f (x:xs'@(x':x'':xs)) = 10*(10*x + x') + x'' : f xs'

%Y Cf. A136414, A193492, A193493.

%K nonn,base

%O 1,1

%A _Reinhard Zumkeller_, Jul 28 2011