OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
f:= 'f':
f(1):= 2: f(2):= 3: f(3):= (1, 2, 3):
S:= [1];
for i from 1 to 5 do T:= map(f, S); U:= map(f, T); S:= map(f, U); od:
select(t -> S[t+1]=1, [$0..nops(S)-1]); # Robert Israel, May 07 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jul 09 2018
STATUS
approved