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.

A153582 A024581 / [1,2,3,...].

Original entry on oeis.org

1, 1, 3, 9, 24, 65, 177, 481, 1308, 3555, 9664, 26269, 71406, 194103, 527625, 1434235, 3898654, 10597641, 28807374, 78306562, 212859305, 578611580, 1572829344, 4275393425, 11621724256, 31591121861, 85873572496, 233428571660, 634524644587, 1724816811090, 4688538195006, 12744768177522
Offset: 0

Views

Author

Gary W. Adamson, Dec 28 2008

Keywords

Comments

Convolved with [1, 2, 3, ...] = A024581: (1, 3, 8, 22, 60, 163, ...) (cf. triangle A153583).

Examples

			(1, 1, 3, 9) convolved with (1, 2, 3, 4) = (4 + 3 + 6 + 9 ) = 22 = A024581(3).
		

Crossrefs

Programs

  • PARI
    lista(nn) = {my(va = vector(nn), vc = vector(nn)); va[1] = 1; for (n=1, nn, if (n > 1, va[n] = round(exp(1)*va[n-1])); vc[n] = va[n] - sum(k=1, n-1, vc[k]*(n-k+1));); vc;} \\ Michel Marcus, Jan 27 2019

Formula

A024581 / [1,2,3,...], where A024581 = (1, 3, 8, 22, 60, 163, ...).

Extensions

More terms from Michel Marcus, Jan 27 2019

A331028 Partition the terms of the harmonic series into groups sequentially so that the sum of each group is equal to or minimally greater than 1; then a(n) is the number of terms in the n-th group.

Original entry on oeis.org

1, 3, 8, 22, 60, 163, 443, 1204, 3273, 8897, 24184, 65739, 178698, 485751, 1320408, 3589241, 9756569, 26521104, 72091835, 195965925, 532690613, 1448003214, 3936080824, 10699376979, 29083922018, 79058296722, 214902731368, 584166189564, 1587928337892, 4316436745787
Offset: 1

Views

Author

Keywords

Comments

a(n) is equal to A024581(n) through a(10), and grows very similarly for n > 10.
Let b(n) = Sum_{j=1..n} a(n); then for n >= 2 it appears that b(n) = round((b(n-1) + 1/2)*e). Cf. A331030. - Jon E. Schoenfield, Jan 14 2020

Examples

			a(1)=1 because 1 >= 1,
a(2)=3 because 1/2 + 1/3 + 1/4 = 1.0833... >= 1, etc.
		

Crossrefs

Some sequences in the same spirit as this: A002387, A004080, A055980, A115515.

Programs

  • PARI
    default(realprecision, 10^5); e=exp(1);
    lista(nn) = {my(r=1); print1(r); for(n=2, nn, print1(", ", -r+(r=floor(e*r+(e+1)/2+(e-1/e)/(24*(r+1/2)))))); } \\ Jinyuan Wang, Mar 31 2020
  • Python
    x = 0.0
    y = 0.0
    for i in range(1,100000000000000000000000):
      y += 1
      x = x + 1/i
      if x >= 1:
        print(y)
        y = 0
        x = 0
    

Formula

a(n) = min(p): Sum_{b=r+1..p+r} 1/b >= 1, r = Sum_{k=1..n-1} a(k), a(1) = 1.

Extensions

a(20)-a(21) from Giovanni Resta, Jan 14 2020
More terms from Jinyuan Wang, Mar 31 2020

A153583 Convolution triangle by rows, A004736 * (A153582 * 0^(n-k)).

Original entry on oeis.org

1, 2, 1, 3, 2, 3, 4, 3, 6, 9, 5, 4, 9, 18, 24, 6, 5, 12, 27, 48, 65, 7, 6, 15, 36, 72, 130, 177, 8, 7, 18, 45, 96, 195, 354, 481, 9, 8, 21, 54, 120, 260, 531, 962, 1308, 10, 9, 24, 63, 144, 325, 708, 1443, 2616, 3555, 11, 10, 27, 72, 168, 390, 885, 1924, 3924, 7110, 9664
Offset: 0

Views

Author

Gary W. Adamson, Dec 28 2008

Keywords

Comments

Row sums = A024581: (1, 3, 8, 22, 60, 163,...).
Right border = A153582.

Examples

			First few rows of the triangle =
  1;
  2, 1;
  3, 2, 3;
  4, 3, 6, 9;
  5, 4, 9, 18, 24;
  6, 5, 12, 27, 48, 65;
  7, 6, 15, 36, 72, 130, 177;
  8, 7, 18, 45, 96, 195, 354, 481;
  9, 8, 21, 54, 120, 260, 531, 962, 1308;
  10, 9, 24, 63, 144, 325, 708, 1443, 2616, 3555;
  ...
Row 3 = (4, 3, 6, 9) = termwise products of (4, 3, 2, 1) and (1, 1, 3, 9);
where A153582 = (1, 1, 3, 9, 24, 65,...).
		

Crossrefs

Programs

  • PARI
    tabl(nn) = {my(va = vector(nn), vc = vector(nn)); va[1] = 1; for (n=1, nn, if (n > 1, va[n] = round(exp(1)*va[n-1])); vc[n] = va[n] - sum(k=1, n-1, vc[k]*(n-k+1)); print(vector(n, k, vc[k]*(n-k+1))););} \\ Michel Marcus, Jan 28 2019

Formula

Convolution triangle by rows, A004736 * (A153582 * 0^(n-k)).

Extensions

More terms from Michel Marcus, Jan 28 2019

A095716 a(n) = integer nearest Pi*a(n-1), where a(0) = 1.

Original entry on oeis.org

1, 3, 9, 28, 88, 276, 867, 2724, 8558, 26886, 84465, 265355, 833637, 2618948, 8227668, 25847981, 81203827, 255109346, 801449647, 2517828323, 7909990963, 24849969499, 78068481620, 245259368334, 770505029782, 2420612941117
Offset: 0

Views

Author

Herman Jamke (hermanjamke(AT)fastmail.fm), Jul 07 2004

Keywords

Crossrefs

Cf. A024581.

Programs

  • Mathematica
    a[0] = 1; a[n_] := Round[Pi*a[n - 1]]; Table[a[n], {n, 0, 30}] (* Clark Kimberling, Aug 18 2012 *)
Showing 1-4 of 4 results.