New answers tagged number-sequence
3
b) The shortest sequence is
Method:
3
Answer to part c):
Found with the following Python code:
from heapq import heappush, heappop
best_n = 0
candidates = [(1, [1], set((1,)))]
while candidates:
prev_max, prev_list, prev_set = heappop(candidates)
n = len(prev_list) + 1
max_n = min(set(range(1, (n+1)+1)) - prev_set) - 1
if max_n > best_n:
best_n = max_n
...
0
maybe 21 wasn't a mistake.
21,91,171,231,351,561,741 etcc
are triangular numbers with cadence 1, obtained from the progressive arithmetic sum 1 + 2 + 3 + 4 + 5 + 6 ..... from the sequence it is clear that 21 is obtained from (6 + 1) * (6/2) and that the other numbers are obtained by the formula (x + 1 + k) * (x + k) /2
where x = 6
k=(+7,+5,+3,+5 ) repeted n ...
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