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Ramanujan's sum. In number theory, Ramanujan's sum, usually denoted cq ( n ), is a function of two positive integer variables q and n defined by the formula. where ( a, q) = 1 means that a only takes on values coprime to q . Srinivasa Ramanujan mentioned the sums in a 1918 paper. [ 1]
The multiplicative inverse of its generating function is the Euler function; by Euler's pentagonal number theorem this function is an alternating sum of pentagonal number powers of its argument. Srinivasa Ramanujan first discovered that the partition function has nontrivial patterns in modular arithmetic , now known as Ramanujan's congruences .
1729 (number) 1729 is the natural number following 1728 and preceding 1730. It is the first nontrivial taxicab number, expressed as the sum of two cubic numbers in two different ways. It is also known as the Ramanujan number or Hardy–Ramanujan number, named after G. H. Hardy and Srinivasa Ramanujan .
Srinivasa Ramanujan[ a] (22 December 1887 – 26 April 1920) was an Indian mathematician. Though he had almost no formal training in pure mathematics, he made substantial contributions to mathematical analysis, number theory, infinite series, and continued fractions, including solutions to mathematical problems then considered unsolvable.
In number theory and combinatorics, a partition of a non-negative integer n, also called an integer partition, is a way of writing n as a sum of positive integers. Two sums that differ only in the order of their summands are considered the same partition. (If order matters, the sum becomes a composition .)
The Ramanujan tau function, studied by Ramanujan ( 1916 ), is the function defined by the following identity: where q = exp (2πiz) with Im z > 0, is the Euler function, η is the Dedekind eta function, and the function Δ (z) is a holomorphic cusp form of weight 12 and level 1, known as the discriminant modular form (some authors, notably ...
In mathematics, Ramanujan's congruences are the congruences for the partition function p ( n) discovered by Srinivasa Ramanujan : In plain words, e.g., the first congruence means that If a number is 4 more than a multiple of 5, i.e. it is in the sequence. 4, 9, 14, 19, 24, 29, . . . then the number of its partitions is a multiple of 5.
Divisor functions were studied by Ramanujan, who gave a number of important congruences and identities; these are treated separately in the article Ramanujan's sum. A related function is the divisor summatory function, which, as the name implies, is a sum over the divisor function.