You can put this solution on YOUR website! When the answers are not 'obvious' I try a few things to whiitle down what I think will or 'work.
This one does not look arithmetic. The numbers climb too fast. So it 'feels' like we need to be multiplying by something or doing something exponential.
Start with the last two numbers = hmmm, 43 is just one more than 42.
Let's do = hey! again we get a number one greater than the lower number in the pair.
Does that work for the entire sequence? In this case, yes
Each successive number is the previous number times (the previous number+1)
I wish I could tell you there is magic formula here. But I haven;t found one. It is more a matter of doing a few and getting a feel for what to try if something just doesn;t jump rite out at you
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