

A110401


a(1) = 999, a(n) is the number obtained by concatenating product of neighboring digits of the previous term.


0



999, 8181, 888, 6464, 242424, 88888, 64646464, 24242424242424, 8888888888888, 646464646464646464646464, 2424242424242424242424242424242424242424242424, 888888888888888888888888888888888888888888888
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

If one uses any other number as a(1), the sequence either comes to an end with a singledigit term or eventually contains increasing strings of 8, 64 and 24 repeatedly. E.g., a(1) = 1234 gives 1234, 2612, 1262, 21212, 2222, 444, 1616, 666, 3636, 181818, 88888, 64646464, 24242424242424, 8888888888888, ...


LINKS



PROG

(PARI) f(n) = my(d=digits(n), nd=[]); for (k=1, #d1, nd = concat(nd, digits(d[k]*d[k+1]))); fromdigits(nd);


CROSSREFS



KEYWORD

base,easy,nonn


AUTHOR



EXTENSIONS



STATUS

approved



