How can i prove that if n>=1, (n(n+1)(2n+1))/6 is an integer. The hint is to use the division algorithm such that n has one of the forms 6k,6k+1,..6k+5 and to work each case.......I tried changing n to 6k but i failed immeaditely :((adsbygoogle = window.adsbygoogle || []).push({});

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# Proof by div alg.

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