E243 -- Observatio de summis divisorum

(An observation on the sums of divisors)

(based on Jordan Bell's abstract)
This is partly a re-run of E152 and E175. Euler gives a recurrence relation that gives the sum of the divisors of a positive integer constructed via the pentagonal numbers.

According to the records, it was presented to the St. Petersburg Academy on April 6, 1752.

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