Question 925738
#1 pattern you found;
#2 Notice differences are in order, 3, 5, 7, so you expect the next difference to be  9.   ;


#3 strange;
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{{{5=5}}}
{{{20=2*2*5}}}
{{{45=3*3*5}}}
{{{80=2*2*2*2*5}}}
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{{{5=1*1*5}}}
{{{20=2^2*5}}}
{{{45=3^2*5}}}
{{{80=4^2*5}}}
5 multiplied by the square of the index for each term.