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.

Showing 1-3 of 3 results.

A268127 a(n) = (A005704(n)-A006047(n))/3.

Original entry on oeis.org

0, 0, 0, 1, 1, 1, 3, 3, 3, 7, 8, 9, 12, 13, 14, 19, 20, 21, 30, 33, 36, 42, 45, 48, 57, 60, 63, 79, 86, 93, 103, 111, 119, 132, 141, 150, 168, 180, 192, 209, 222, 235, 257, 271, 285, 316, 335, 354, 380, 400, 420, 453, 474, 495, 543, 573, 603, 639, 672, 705, 747
Offset: 0

Views

Author

Tom Edgar, Jan 26 2016

Keywords

Crossrefs

Programs

  • Mathematica
    b[n_] := b[n] = If[n <= 2, n+1, b[n-1] + b[Floor[n/3]]];
    c = Nest[Join[#, 2#, 3#]&, {1}, 4];
    a[n_] := (b[n] - c[[n+1]])/3;
    Table[a[n], {n, 0, 60}] (* Jean-François Alcover, Dec 12 2018 *)
  • Sage
    def b(n):
        A=[1]
        for i in [1..n]:
            A.append(A[i-1] + A[floor(i/3)])
        return A[n]
    [(b(n)-prod(x+1 for x in n.digits(3)))/3 for n in [0..60]]

Formula

Let b(0) = 1 and b(n) = b(n-1) + b(floor(n/3)) and let c(n) = Product_{i=0..k}(n_i+1) where n = Sum_{i=0..k}n_i*3^i is the ternary representation of n. Then a(n) = (1/3)*(b(n) - c(n)).

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

Views

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)).

A270774 a(n) = (A005706(n) - A194459(n))/5.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 3, 3, 3, 3, 3, 6, 6, 6, 6, 6, 10, 10, 10, 10, 10, 16, 17, 18, 19, 20, 23, 24, 25, 26, 27, 32, 33, 34, 35, 36, 43, 44, 45, 46, 47, 56, 57, 58, 59, 60, 73, 76, 79, 82, 85, 91, 94, 97, 100, 103, 112, 115, 118, 121
Offset: 0

Views

Author

Tom Edgar, Mar 22 2016

Keywords

Comments

A combinatorial interpretation is given in the Edgar link.

Crossrefs

Programs

  • Mathematica
    b[0] = 1; b[n_] := b[n] = b[n-1] + b[Floor[n/5]];
    c[n_] := If[OddQ[n], 2 Count[Table[Binomial[n, k], {k, 0, (n-1)/2}], c_ /; !Divisible[c, 5]], 2 Count[Table[Binomial[n, k], {k, 0, (n-2)/2}], c_ /; !Divisible[c, 5]] + Boole[!Divisible[Binomial[n, n/2], 5]]];
    a[n_] := (b[n] - c[n])/5;
    Table[a[n], {n, 0, 63}] (* Jean-François Alcover, Feb 15 2019 *)
  • Sage
    def b(n):
        A=[1]
        for i in [1..n]:
            A.append(A[i-1] + A[i//5])
        return A[n]
    print([(b(n)-prod(x+1 for x in n.digits(5)))/5 for n in [0..63]])

Formula

Let b(0) = 1 and b(n) = b(n-1) + b(floor(n/5)) and let c(n) = Product_{i=0..k}(n_i+1) where n = Sum_{i=0..k}n_i*5^i is the base 5 representation of n. Then a(n) = (1/5)*(b(n) - c(n)).
Showing 1-3 of 3 results.