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 21-24 of 24 results.

A304791 Expansion of Product_{k>=1} (1 - prime(k)*x^k).

Original entry on oeis.org

1, -2, -3, 1, 3, 18, 0, 35, -27, -85, -91, -109, -366, 118, 942, -957, 2791, 2091, 4855, -1157, -6903, 3341, 3162, -37034, -46480, -89890, 581, 131275, -296935, 167543, 108671, 801491, 616017, 2441581, -307733, -1864550, 4495872, 1158228, -2589768, -767646, -21062537
Offset: 0

Views

Author

Ilya Gutkovskiy, May 18 2018

Keywords

Comments

Convolution inverse of A145519.

Crossrefs

Programs

  • Mathematica
    nmax = 40; CoefficientList[Series[Product[(1 - Prime[k] x^k), {k, 1, nmax}], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[-Sum[d Prime[d]^(k/d), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 40}]

Formula

G.f.: Product_{k>=1} (1 - A000040(k)*x^k).

A147879 Expansion of Product_{k>=1} (1 + x^k*A005185(k)).

Original entry on oeis.org

1, 1, 1, 3, 5, 8, 12, 21, 29, 49, 73, 105, 162, 236, 338, 502, 706, 984, 1441, 1998, 2800, 3934, 5472, 7407, 10210, 14053, 19066, 25986, 35134, 47010, 63739, 85008, 112610, 150861, 200133, 264838, 349587, 459970, 602763, 792220, 1034136, 1345530
Offset: 0

Views

Author

Roger L. Bagula, Nov 16 2008

Keywords

Crossrefs

Programs

  • Mathematica
    f[n_Integer?Positive] := f[n] = f[n - f[n - 1]] + f[n - f[n - 2]]; f[0] = 0; f[1] = f[2] = 1; (* A005185 *)
    nmax = 41; CoefficientList[Series[Product[(1 + f[k] * x^k), {k, 1, nmax}], {x, 0, nmax}], x] (* Georg Fischer, Dec 10 2020 *)
  • PARI
    \\ here B(n) is A005185 as vector.
    B(n)={my(A=vector(n, k, 1)); for(k=3, n, A[k]= A[k-A[k-1]]+ A[k-A[k-2]]); A}
    seq(n)=my(v=B(n)); {Vec(prod(k=1, #v, 1 + x^k*v[k] + O(x*x^n)))} \\ Andrew Howroyd, Dec 10 2020

Extensions

Definition corrected by Georg Fischer, Dec 10 2020

A152006 Expansion of Product_{k > 0} (1 + f(k)*x^k), where f(1) = 1 and f(m) = prime(m-1) for m >= 2.

Original entry on oeis.org

1, 1, 2, 5, 8, 18, 34, 63, 102, 203, 336, 589, 999, 1675, 2799, 4768, 7561, 12224, 20513, 31724, 51621, 81976, 128560, 199192, 312536, 482806, 744847, 1147952, 1755931, 2649474, 4051413, 6069450, 9105323, 13747364, 20335077, 30508629, 45198631
Offset: 0

Views

Author

Roger L. Bagula, Nov 19 2008

Keywords

Crossrefs

Programs

  • Mathematica
    f[n_] = If[n < 2, n, Prime[n - 1]];
    P[x_, n_] := P[x, n] = Product[1 + f[m]*x^m, {m, 0, n}];
    Take[CoefficientList[P[x, 37], x],37]
    (* Program edited and corrected by Petros Hadjicostas, Apr 12 2020 *)

Formula

a(n) = [x^n] Product_{k > 0} (1 + f(k)*x^k), where f(1) = 1 and f(m) = prime(m-1) for m >= 2.

Extensions

Various sections edited by Petros Hadjicostas, Apr 12 2020

A371310 Expansion of e.g.f. Product_{k>=1} (1 + prime(k)*x^k/k!).

Original entry on oeis.org

1, 2, 3, 23, 47, 231, 2260, 6527, 35151, 224759, 3434124, 12476055, 79758206, 491191521, 4752819625, 105146082344, 393097093065, 2976053272527, 21569670506914, 188844207315245, 2277243901499454, 72603521472295945, 326137558352646889, 2491611720654851668
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 24 2024

Keywords

Comments

"EFJ" (unordered, size, labeled) transform of primes.

Crossrefs

Programs

  • Mathematica
    nmax = 23; CoefficientList[Series[Product[(1 + Prime[k] x^k/k!), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
Previous Showing 21-24 of 24 results.