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Double a triangle (Posted on 2015-02-19) Difficulty: 3 of 5
In the sequence of triangular numbers, some numbers are twice another.

For example t(20)=210 which is twice t(14)=105.

Characterize all such numbers.

Easy bonus: Explain why (except for the trivial case) there are no square numbers that are twice another.

No Solution Yet Submitted by Jer    
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  Subject Author Date
Some ThoughtsOne more observationBrian Smith2016-07-30 11:24:32
Solutionon triangular doublesAdy TZIDON2015-02-19 15:14:31
Some ThoughtsThe first few pairsCharlie2015-02-19 14:07:43
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