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 1-4 of 4 results.

A349016 G.f. A(x) satisfies: A(x) = 1 + x * A(-x) / (1 - x) + x * A(x)^2.

Original entry on oeis.org

1, 2, 3, 12, 26, 125, 317, 1642, 4492, 24188, 69174, 381613, 1123923, 6304781, 18962485, 107682542, 329007674, 1885923378, 5833166568, 33685017384, 105214504816, 611241171298, 1924588709710, 11236434464097, 35617302886643, 208815253200975, 665665428686531
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 05 2021

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 26; A[] = 0; Do[A[x] = 1 + x A[-x]/(1 - x) + x A[x]^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
    a[0] = 1; a[n_] := a[n] = Sum[a[k] ((-1)^k + a[n - k - 1]), {k, 0, n - 1}]; Table[a[n], {n, 0, 26}]

Formula

a(0) = 1; a(n) = Sum_{k=0..n-1} a(k) * ((-1)^k + a(n-k-1)).

A349014 G.f. A(x) satisfies: A(x) = 1 + x + x^2 * A(x) / (1 - x) + x^2 * A(x)^2.

Original entry on oeis.org

1, 1, 2, 4, 9, 20, 47, 111, 270, 663, 1656, 4174, 10636, 27308, 70651, 183902, 481436, 1266515, 3346793, 8879116, 23642034, 63156917, 169222939, 454660940, 1224650739, 3306338583, 8945780742, 24252558183, 65872671839, 179228552638, 488443704486
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 05 2021

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 30; A[] = 0; Do[A[x] = 1 + x + x^2 A[x]/(1 - x) + x^2 A[x]^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
    a[0] = a[1] = 1; a[n_] := a[n] = Sum[a[k] (1 + a[n - k - 2]), {k, 0, n - 2}]; Table[a[n], {n, 0, 30}]

Formula

a(0) = a(1) = 1; a(n) = Sum_{k=0..n-2} a(k) * (1 + a(n-k-2)).
a(n) ~ sqrt(1/r + (2-r)*s/(1-r)^2 + 2*s^2) / (2*sqrt(Pi)*n^(3/2)*r^n), where r = 0.3495518575342322867499973927570340375314361958565... and s = 3.323404276086477625771682790702806844309937221726... are real roots of the system of equations 1 + r + r^2*s*(1/(1-r) + s) = s, r^2*(1/(1-r) + 2*s) = 1. - Vaclav Kotesovec, Nov 06 2021

A349015 G.f. A(x) satisfies: A(x) = 1 + x * A(x) / (1 - x) - x * A(x)^2.

Original entry on oeis.org

1, 0, 1, 0, 2, -1, 5, -6, 16, -28, 62, -125, 267, -565, 1213, -2618, 5686, -12418, 27248, -60048, 132848, -294930, 656878, -1467257, 3286219, -7378239, 16603459, -37441989, 84599855, -191501531, 434224405, -986161958, 2243009870, -5108859820, 11651743902
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 05 2021

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 34; A[] = 0; Do[A[x] = 1 + x A[x]/(1 - x) - x A[x]^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
    a[0] = 1; a[n_] := a[n] = Sum[a[k] (1 - a[n - k - 1]), {k, 0, n - 1}]; Table[a[n], {n, 0, 34}]

Formula

a(0) = 1; a(n) = Sum_{k=0..n-1} a(k) * (1 - a(n-k-1)).
a(n) = 1 - Sum_{k=0..n-1} (-1)^k * A007477(k).
a(n) ~ 3^(1 + n) * (1/((1 - 2/(19 - 3*sqrt(33))^(1/3) - (1/2)*(19 - 3*sqrt(33))^(1/3))^n * ((19 - 3*sqrt(33))^(1/6)*(2 + (19 - 3*sqrt(33))^(1/3))^2 * n^(3/2) * sqrt(((-1951699 + 339747*sqrt(33))*Pi) / (-70717234 + 12310290*sqrt(33) + (19 - 3*sqrt(33))^(2/3) * (-3903398 + 679494*sqrt(33)) + (19 - 3*sqrt(33))^(1/3) * (-35358617 + 6155145*sqrt(33))))))). - Vaclav Kotesovec, Nov 17 2021

A376317 a(n) = P(n+1, n+1) where P(n, m) = P(n, m-1) + P(n-1, m + f(m-n)) for n < m with P(n, m) = P(n-1, m) for 0 <= m <= n and P(0, m) = 1 for m >= 0 and where f(n) = [(n mod 4) > 0].

Original entry on oeis.org

1, 2, 6, 23, 100, 466, 2270, 11413, 58776, 308473, 1643922, 8872220, 48393710, 266357916, 1477471248, 8251090171, 46353709956, 261783417427, 1485374891782, 8463626764923, 48408809202918, 277834282516061, 1599585546691518, 9235769089804804, 53466364700486982
Offset: 0

Views

Author

Mikhail Kurkov, Sep 22 2024

Keywords

Comments

Conjecture: cases f(n) = n mod 2 and f(n) = [(n mod 3) > 0] both gives A006318.

Crossrefs

Programs

  • PARI
    upto(n) = my(v1); v1 = vector(2*(n+1), i, 1); v2 = vector(n+1, i, 0); v2[1] = 1; for(i=1, n, for(j=i+1, 2*(n+1)-i, v1[j] = v1[j+(((j-i)%4)>0)] + v1[j-1]); v2[i+1] = v1[i+1]); v2

Formula

Conjecture: a(n+2) = a(n) + A215973(n+2) - A215973(n+1) (noticed by advanced OEIS search).
Recurrence: (n+1)*a(n) = 4*(2*n-1)*a(n-1) - (11*n-25)*a(n-2) - 2*(2*n+5)*a(n-3) + 12*(n-2)*a(n-4) - 2*(2*n-7)*a(n-5). - Vaclav Kotesovec, Sep 23 2024
Showing 1-4 of 4 results.