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A045777
a(1)=1, a(2)=2; thereafter successive products of pairs of digits make further digits.
2
1, 2, 2, 4, 8, 3, 2, 2, 4, 6, 4, 8, 2, 4, 2, 4, 3, 2, 1, 6, 8, 8, 8, 1, 2, 6, 2, 6, 4, 8, 6, 4, 6, 4, 8, 2, 1, 2, 1, 2, 1, 2, 2, 4, 3, 2, 4, 8, 2, 4, 2, 4, 2, 4, 3, 2, 1, 6, 2, 2, 2, 2, 2, 2, 4, 8, 1, 2, 6, 8, 3, 2, 1, 6, 8, 8, 8, 8, 8, 1, 2, 6, 2, 6, 1, 2, 4, 4, 4, 4, 4, 8, 3, 2, 8, 2, 1, 2, 4, 8, 2, 4, 6, 2, 6
OFFSET
1,2
COMMENTS
The numbers 0, 5, 7, and 9 never appear, but arbitrarily long sequences of 8's appear.
LINKS
EXAMPLE
1*2=2 2*2=4 2*4=8 4*8=32 8*3=24...
MATHEMATICA
t = {1, 2}; Do[ t = Join[t, IntegerDigits[t[[n-1]] t[[n-2]]]], {n, 3, 100}]; t
PROG
(Python)
from itertools import islice
from collections import deque
def agen(): # generator of terms
a = deque([1, 2])
while True:
a.extend(list(map(int, str(a[0]*a[1]))))
yield a.popleft()
print(list(islice(agen(), 105))) # Michael S. Branicky, Feb 15 2024
CROSSREFS
Sequence in context: A131199 A112059 A093094 * A136534 A121175 A368515
KEYWORD
easy,nonn,base
STATUS
approved