OFFSET
1,1
COMMENTS
The "waterfall" sequence S for a given starting value S(1) > 9 is defined as S(n) = d(n)*d(n-1) (n > 1), where d(n) is the n-th digit of the sequence.
LINKS
E. Angelini, Waterfalls (of multiplications), Mar 27 2012
E. Angelini, Waterfalls (of multiplications) [Cached copy, with permission]
PROG
(PARI) is_A210652(n, L=2e3)={ my(S=eval(Vec(Str(n)))); for(i=1, L, (S=concat(vecextract(S, "^1"), eval(Vec(Str(n=S[1]*S[2]))))) | return(1))} \\ The optional 2nd parameter L is the limit prior to which the remaining digits must be all zero. The result may be wrong if L is not large enough, but large values of L yield slow computations for values NOT in this sequence.
for(n=10, 999, is_A210652(n) & print1(n", "))
CROSSREFS
KEYWORD
nonn,base
AUTHOR
M. F. Hasler, Mar 27 2012
STATUS
approved