OFFSET
0,4
COMMENTS
Sorted tetranacci numbers, a.k.a. sorted Fibonacci 4-step sequence.
As found by T. D. Noe: Max=4556699. Cycle period=41652. Cycle starts with the 23944th term.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
Richard I. Hess, Problem 920: sorted Fibonacci sequence, Pi Mu Epsilon Journal, Vol. 10 (Fall 1998) No. 9, pp. 754-755.
EXAMPLE
a(8) = SORT[a(4) + a(5) + a(6) + a(7)] = SORT[108] = 18.
a(10) = SORT[a(6) + a(7) + a(8) + a(9)] = SORT[221] = 122.
MATHEMATICA
nxt[{a_, b_, c_, d_, e_}]:={b, c, d, e, FromDigits[Sort[DeleteCases[ IntegerDigits[ b+c+d+e], _?0]]]}; NestList[nxt, {0, 1, 1, 2, 4}, 50][[All, 1]] (* Harvey P. Dale, Jan 17 2022 *)
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jonathan Vos Post, Jun 10 2005
STATUS
approved