OFFSET
1,1
COMMENTS
This definition of "undulating" is more restrictive than the one used in A033619 and excludes single-digit numbers and numbers of the pattern aaaaaa. - R. J. Mathar, Jun 15 2007
REFERENCES
Jason Earls, Red Zen, Lulu Press, NY, 2006, pp. 56-57. ISBN: 978-1-4303-2017-3.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..2146
MATHEMATICA
undHarsQ[n_] := Module[{d = IntegerDigits[n]}, Divisible[n, Plus @@ d] && Length @ Union[d] > 1 && Length @ Union[d[[1 ;; -1 ;; 2]]] == 1 && Length @ Union[d[[2 ;; -1 ;; 2]]] == 1 ]; Select[Range[40000], undHarsQ] (* Amiram Eldar, Jan 27 2021 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Jason Earls, May 25 2007
EXTENSIONS
More terms from R. J. Mathar, Jun 15 2007
STATUS
approved