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RainbowBlues ∙
Or alternatively:
½ n2 + ½ n
or:
½ (n2+n)
a more simple answer is
(n2 ÷ 2)+½ n
e.g:- 10x10=100
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2=50+5=55
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The nth triangular number is 0.5*n*(n+1)
The Nth term formula for oblong numbers is N = N(N+1)
It is T/2 * (t+1)
t(n) = n*(n+1)/2
The nth term of the sequence is expressed by the formula 8n - 4.