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what's the relation between these numbers 1,2,4,9,16,25,36,...

  • Math -

    Think "squares."

  • Maths -

    The subject is maths.

    These are positive integers n such that the sum of the divisors of n, excluding 1, is a multiple of the number of divisors of n.

    so the next numbers in the sequence are

    64, 81, 100, 121, 289,

    As examples
    The 9 divisors of 36 are {1,2,3,4,6,9,12,18,36}, giving sum (1+2+3=4+6+9+12+18+36)-1=90 which is a multiple of 9. Thus 36 is a term of the sequence.

    The 3 divisors of 25 are
    {1,5,25} giving a sum (1+5+25)-1=30 which is a multiple of 3. Thus 25 is a term of the sequence.

  • college -

    it's not square cuz i want the relation btw these numbers 1,2,4,9,16,25,36,.. NOT btw these numbers 1,4,9,16,25,...

  • maths -

    Agreed it is not squares. It is the sequence as I described above.

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