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.

Previous Showing 21-23 of 23 results.

A338848 Number of compositions (ordered partitions) of n into distinct powers of 3.

Original entry on oeis.org

1, 1, 0, 1, 2, 0, 0, 0, 0, 1, 2, 0, 2, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 0, 2, 6, 0, 0, 0, 0, 2, 6, 0, 6, 24, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 0, 2, 6, 0, 0, 0, 0, 2, 6
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 11 2020

Keywords

Crossrefs

Programs

  • PARI
    a(n) = my(c=0,r); while(n, [n,r]=divrem(n,3); if(r==2,return(0)); c+=r); c!; \\ Kevin Ryde, Nov 14 2020

Formula

a(n) = A039966(n) * A062756(n)!. - Kevin Ryde, Nov 14 2020

A374626 Expansion of Product_{k>=0} 1 / (1 - 3*x^(3^k)).

Original entry on oeis.org

1, 3, 9, 30, 90, 270, 819, 2457, 7371, 22143, 66429, 199287, 597951, 1793853, 5381559, 16144947, 48434841, 145304523, 435914388, 1307743164, 3923229492, 11769690933, 35309072799, 105927218397, 317781662562, 953344987686, 2860034963058, 8580104911317
Offset: 0

Views

Author

Seiichi Manyama, Jul 14 2024

Keywords

Crossrefs

For generating functions Product_{k>=0} 1 / (1 - a*x^(b^k)) for the following values of (a,b) see: (1,2) A018819, (1,3) A062051, (2,2) A309728.
Cf. A117940.

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(1/prod(k=0, logint(N,3), 1-3*x^3^k))

Formula

G.f. A(x) satisfies A(x) = A(x^3)/(1 - 3*x).
a(n) is divisible by 3 for n > 0.

A374627 Expansion of Product_{k>=0} 1 / (1 - x^(3^k))^3.

Original entry on oeis.org

1, 3, 6, 13, 24, 39, 64, 99, 144, 212, 303, 417, 578, 786, 1041, 1382, 1809, 2322, 2985, 3798, 4761, 5973, 7434, 9144, 11247, 13743, 16632, 20126, 24225, 28929, 34541, 41061, 48489, 57242, 67320, 78723, 92029, 107238, 124350, 144151, 166641, 191820, 220729, 253368, 289737, 331218, 377811
Offset: 0

Views

Author

Seiichi Manyama, Jul 14 2024

Keywords

Crossrefs

Programs

  • PARI
    my(N=50, x='x+O('x^N)); Vec(1/prod(k=0, logint(N, 3), 1-x^3^k)^3)

Formula

G.f. A(x) satisfies A(x) = A(x^3)/(1 - x)^3.
Previous Showing 21-23 of 23 results.