OFFSET
0,4
COMMENTS
The maximum value in this sequence is 667. After the 75th term, the next 120 terms (a(76) - a(195)) repeat as a group infinitely.
LINKS
Zak Seidov, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = SORT[a(n-1) + a(n-2)].
EXAMPLE
a(8)=12 because a(7)+a(6)=13+8=21 and the digits of 21 sorted in ascending order = 12.
Also a(17)=4 because a(16)+a(15)=15+25=40 and the digits of 40 sorted in ascending order = 04, or just 4;
MAPLE
a:= proc(n) option remember; `if`(n<2, n, parse(cat(
sort(convert(a(n-1)+a(n-2), base, 10))[])))
end:
seq(a(n), n=0..77); # Alois P. Heinz, Aug 31 2022
MATHEMATICA
a[0]:=0
a[1]:=1
a[n_] := a[n]=FromDigits[Sort[IntegerDigits[a[n-1]+a[n-2]]]] (* Peter J. C. Moses, Feb 08 2014 *)
nxt[{a_, b_}]:={b, FromDigits[Sort[IntegerDigits[a+b]]]}; NestList[nxt, {0, 1}, 70][[All, 1]] (* Harvey P. Dale, Jul 27 2020 *)
PROG
(Python)
a, terms = [0, 1], 66
[a.append(int("".join(sorted(str(a[-2]+a[-1]))))) for n in range(2, terms)]
print(a) # Michael S. Branicky, Aug 31 2022
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Gil Broussard, Jan 16 2004
STATUS
approved