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if the last digit of a number is 3 or 7, its square ends in an even digit followed by a 9; if the last digit of a number is 4 or 6, its square ends in an odd digit followed by a 6; and; if the last digit of a number is 5, its square ends in 25. In base 12, a square number can end only with square digits (like in base 12, a prime number can end ...
In their book, Kathleen Ollerenshaw and David S. Brée give a method of construction and enumeration of all most-perfect magic squares. They also show that there is a one-to-one correspondence between reversible squares and most-perfect magic squares. For n = 36, there are about 2.7 × 10 44 essentially different most-perfect magic squares.
Every even perfect number ends in 6 or 28, base ten; and, with the only exception of 6, ends in 1 in base 9. [55] [56] Therefore, in particular the digital root of every even perfect number other than 6 is 1. The only square-free perfect number is 6. [57]
[7] [8] [9] It is widely believed, [10] but not proven, that no odd perfect numbers exist; numerous restrictive conditions have been proven, [10] including a lower bound of 10 1500. [11] The following is a list of all 52 currently known (as of January 2025) Mersenne primes and corresponding perfect numbers, along with their exponents p.
for {complete} the complement of [j i] is at position [j i + k (m/2) ; #k=n ]. for squares: {2 compact 2 complete} is the "modern/alternative qualification" of what Dame Kathleen Ollerenshaw called most-perfect magic square, {n compact n complete} is the qualifier for the feature in more than 2 dimensions.
An odd superperfect number n would have to be a square number such that ... -perfect and m-superperfect numbers are (m,2)-perfect. [4] ... 2 12 2200380, 8801520 ...
RTX earnings call for the period ending September 30, 2024. ... Pratt opened a new 845,000 square foot facility in Oklahoma City that will support global sustainment efforts for military engines ...
According to Guy, Erdős has asked whether there are infinitely many pairs of consecutive powerful numbers such as (23 3, 2 3 3 2 13 2) in which neither number in the pair is a square. Walker (1976) showed that there are indeed infinitely many such pairs by showing that 3 3 c 2 + 1 = 7 3 d 2 has infinitely many solutions.