cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A268443 a(n) = (A005705(n) - A268444(n))/4.

Original entry on oeis.org

0, 0, 0, 0, 1, 1, 1, 1, 3, 3, 3, 3, 6, 6, 6, 6, 11, 12, 13, 14, 17, 18, 19, 20, 25, 26, 27, 28, 35, 36, 37, 38, 49, 52, 55, 58, 64, 67, 70, 73, 82, 85, 88, 91, 103, 106, 109, 112, 130, 136, 142, 148, 158, 164, 170, 176, 190, 196, 202, 208, 226, 232, 238, 244
Offset: 0

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Author

Tom Edgar, Feb 04 2016

Keywords

Crossrefs

Programs

  • Sage
    def b(n):
        A=[1]
        for i in [1..n]:
            A.append(A[i-1] + A[i//4])
        return A[n]
    print([(b(n)-prod(x+1 for x in n.digits(4)))/4 for n in [0..63]])

Formula

Let b(0) = 1 and b(n) = b(n-1) + b(floor(n/4)) and let c(n) = Product_{i=0..k}(n_i+1) where n = Sum_{i=0..k}n_i*4^i is the base 4 representation of n. Then a(n) = (1/4)*(b(n) - c(n)).