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The falling factorial can be extended to real values of using the gamma function provided and + are real numbers that are not negative integers: = (+) (+) , and so can the rising factorial: = (+) . Calculus
All other four-digit numbers eventually reach 6174 if leading zeros are used to keep the number of digits at 4. For numbers with three identical digits and a fourth digit that is one higher or lower (such as 2111), it is essential to treat 3-digit numbers with a leading zero; for example: 2111 – 1112 = 0999; 9990 – 999 = 8991; 9981 – 1899 ...
Ω(n), the prime omega function, is the number of prime factors of n counted with multiplicity (so it is the sum of all prime factor multiplicities). A prime number has Ω( n ) = 1. The first: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37 (sequence A000040 in the OEIS ).
Superior highly composite numbers: 2, 6, 12, 60, 120, 360, 2520, 5040, 55440, 720720, ... A positive integer n for which there is an e > 0 such that d(n) / n e ≥ d(k) / k e for all k > 1. A002201: Pronic numbers: 0, 2, 6, 12, 20, 30, 42, 56, 72, 90, ... a(n) = 2t(n) = n(n + 1), with n ≥ 0 where t(n) are the triangular ...
[1] [5] [6] It is currently an open problem whether there are infinitely many Mersenne primes and even perfect numbers. [ 2 ] [ 6 ] The density of Mersenne primes is the subject of the Lenstra–Pomerance–Wagstaff conjecture , which states that the expected number of Mersenne primes less than some given x is ( e γ / log 2) × log log x ...
In addition, there are no Kaprekar numbers for 5-digit and 7-digit numbers because they do not satisfy the above equations (1)~(5). Furthermore, it is clear that even-digits with greater than or equal to 8, [9] and with 9 digit, [10] or odd-digits with greater than or equal to 15 digits [11] have multiple solutions. Although 11-digit and 13 ...
From this it follows that the rightmost digit is always 0, the second can be 0 or 1, the third 0, 1 or 2, and so on (sequence A124252 in the OEIS).The factorial number system is sometimes defined with the 0! place omitted because it is always zero (sequence A007623 in the OEIS).
42 is a pronic number, [1] an abundant number [2] as well as a highly abundant number, [3] a practical number, [4] an admirable number, [5] and a Catalan number. [6] The 42-sided tetracontadigon is the largest such regular polygon that can only tile a vertex alongside other regular polygons, without tiling the plane. [7] [8] [9] [a]