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  2. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    Name First elements Short description OEIS Mersenne prime exponents : 2, 3, 5, 7, 13, 17, 19, 31, 61, 89, ... Primes p such that 2 p − 1 is prime.: A000043 ...

  3. Four fours - Wikipedia

    en.wikipedia.org/wiki/Four_fours

    For example, when d=4, the hash table for two occurrences of d would contain the key-value pair 8 and 4+4, and the one for three occurrences, the key-value pair 2 and (4+4)/4 (strings shown in bold). The task is then reduced to recursively computing these hash tables for increasing n , starting from n=1 and continuing up to e.g. n=4.

  4. Composition (combinatorics) - Wikipedia

    en.wikipedia.org/wiki/Composition_(combinatorics)

    Note that the ancient Sanskrit sages discovered many years before Fibonacci that the number of compositions of any natural number n as the sum of 1's and 2's is the nth Fibonacci number! Note that these are not general compositions as defined above because the numbers are restricted to 1's and 2's only. 1=1 (1) 2=1+1=2 (2) 3=1+1+1=1+2=2+1 (3) 4 ...

  5. Combination - Wikipedia

    en.wikipedia.org/wiki/Combination

    These combinations (subsets) are enumerated by the 1 digits of the set of base 2 numbers counting from 0 to 2 n − 1, where each digit position is an item from the set of n. Given 3 cards numbered 1 to 3, there are 8 distinct combinations ( subsets ), including the empty set :

  6. Coin problem - Wikipedia

    en.wikipedia.org/wiki/Coin_problem

    For example, if you had two types of coins valued at 6 cents and 14 cents, the GCD would equal 2, and there would be no way to combine any number of such coins to produce a sum which was an odd number; additionally, even numbers 2, 4, 8, 10, 16 and 22 (less than m=24) could not be formed, either.

  7. Jacobi's four-square theorem - Wikipedia

    en.wikipedia.org/wiki/Jacobi's_four-square_theorem

    In particular, for a prime number p we have the explicit formula r 4 (p) = 8(p + 1). [2] Some values of r 4 (n) occur infinitely often as r 4 (n) = r 4 (2 m n) whenever n is even. The values of r 4 (n) can be arbitrarily large: indeed, r 4 (n) is infinitely often larger than ⁡. [2]

  8. List of numbers - Wikipedia, the free encyclopedia

    en.wikipedia.org/wiki/List_of_numbers

    A list of articles about numbers (not about numerals). Topics include powers of ten, notable integers, prime and cardinal numbers, and the myriad system.

  9. Combinatorial number system - Wikipedia

    en.wikipedia.org/wiki/Combinatorial_number_system

    In the example C and C′ correspond to numbers 1001011001 2 = 601 10 and 1010001011 2 = 651 10, which again shows that C comes before C′. This number is not however the one one wants to represent the k -combination with, since many binary numbers have a number of raised bits different from k ; one wants to find the relative position of C in ...