A032981 - OEIS

%I #21 Feb 13 2021 01:12:00

%S 1,2,3,4,5,6,7,8,9,10,11,12,21,22,23,32,33,34,43,44,45,54,55,56,65,66,

%T 67,76,77,78,87,88,89,98,99,100,101,110,111,112,121,122,123,210,211,

%U 212,221,222,223,232,233,234,321,322,323,332,333,334,343,344,345

%N Positive numbers with the property that all pairs of consecutive base-10 digits differ by 0 or 1.

%C a(n) = A178403(n+1) for n < 38. - _Reinhard Zumkeller_, May 27 2010

%H Alois P. Heinz, <a href="/A032981/b032981.txt">Table of n, a(n) for n = 1..10000</a>

%t okQ[n_]:=Max[Abs[Last[#]-First[#]]&/@Partition[IntegerDigits[n],2,1]]<2

%t Select[Range[350],okQ]  (* _Harvey P. Dale_, Feb 14 2011 *)

%o (Haskell)

%o a032981 n = a032981_list !! (n-1)

%o a032981_list = map read $ filter f $ map show [1..] :: [Int] where

%o    f ps = all (`elem` neighbours) $ zipWith ((. return) . (:)) ps (tail ps)

%o    neighbours = "09" : "90" : zipWith ((. return) . (:))

%o       (digs ++ tail digs ++ init digs) (digs ++ init digs ++ tail digs)

%o    digs = "0123456789"

%o -- _Reinhard Zumkeller_, Feb 14 2015

%Y Cf. A068148 (primes).

%K nonn,base

%O 1,2

%A _Clark Kimberling_