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  2. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    "subtract if possible, otherwise add": a(0) = 0; for n > 0, a(n) = a(n − 1) − n if that number is positive and not already in the sequence, otherwise a(n) = a(n − 1) + n, whether or not that number is already in the sequence.

  3. 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]

  4. 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 :

  5. 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 ...

  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. Combinatorial number system - Wikipedia

    en.wikipedia.org/wiki/Combinatorial_number_system

    Continuing similarly to search for a 3-combination at position 16 − 15 = 1 one finds c 3 = 3, which uses up the final unit; this establishes = + + (), and the remaining values c i will be the maximal ones with () =, namely c i = i − 1. Thus we have found the 5-combination {8, 6, 3, 1, 0}.

  8. Doctors Say This Viral "Sleep Rule" Actually Works - AOL

    www.aol.com/lifestyle/doctors-viral-sleep-rule...

    TikTok is filled with tips and tricks — some legitimate, many not — to help you sleep better.One of the latest encourages people to follow a 10-3-2-1-0 sleep rule, which is actually not just ...

  9. Covering system - Wikipedia

    en.wikipedia.org/wiki/Covering_system

    a 1 = 20615674205555510, a 2 = 3794765361567513 (sequence A083216 in the OEIS). In this sequence, the positions at which the numbers in the sequence are divisible by a prime p form an arithmetic progression; for instance, the even numbers in the sequence are the numbers a i where i is congruent to 1 mod 3. The progressions divisible by ...