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 11-17 of 17 results.

A023662 Convolution of odd numbers and primes.

Original entry on oeis.org

2, 9, 24, 51, 96, 165, 264, 399, 576, 805, 1094, 1451, 1886, 2405, 3014, 3723, 4544, 5485, 6554, 7761, 9112, 10615, 12280, 14117, 16140, 18361, 20786, 23421, 26272, 29345, 32658, 36229, 40068, 44183, 48586, 53289, 58300, 63631, 69292
Offset: 1

Views

Author

Keywords

Crossrefs

Cf. A000040, A005408, A061802 (first differences).

Programs

  • Maple
    A023662 := proc(n)
        add( ithprime(n-i)*(2*i+1),i=0..n-1) ;
    end proc: # R. J. Mathar, Nov 29 2015
  • Mathematica
    Table[Sum[Prime[n - k + 1] (2 k - 1), {k, n}], {n, 39}] (* Michael De Vlieger, Nov 29 2015 *)
  • PARI
    a(n) = sum(i=1, n, prime(n-i+1)*(2*i-1)); \\ Michel Marcus, Sep 30 2013

Formula

a(n) = Sum_{i=0..n-1} A000040(n-i)*A005408(i). - R. J. Mathar, Nov 29 2015
a(n) = Sum_{i=0..n-1} A061802(i). - Marco Zárate, Jun 09 2024
From Ridouane Oudra, Feb 19 2025: (Start)
a(n) = Sum_{i=1..n} Sum_{j=1..n} min(prime(i), prime(j)).
a(n) = A167214(n) - A062020(n).
a(n) = 2*A167214(n) - A316322(n).
a(n) = A014148(n) + A014148(n-1).
a(n) = A007504(n) + 2*A014148(n-1). (End)

A023538 Convolution of natural numbers with (1, p(1), p(2), ... ), where p(k) is the k-th prime.

Original entry on oeis.org

1, 4, 10, 21, 39, 68, 110, 169, 247, 348, 478, 639, 837, 1076, 1358, 1687, 2069, 2510, 3012, 3581, 4221, 4934, 5726, 6601, 7565, 8626, 9788, 11053, 12425, 13906, 15500, 17221, 19073, 21062, 23190, 25467, 27895, 30480, 33228, 36143, 39231, 42498, 45946, 49585
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

Formula

a(n) = Sum_{k<=n} [(A158611(k+1)) * (A000027(n-k+1))] = Sum_{k<=n} [(A008578(k)) * (A000027(n-k+1))]. [Jaroslav Krizek, Aug 05 2009; Correction for change of offset in A158611 and A008578 in Aug 2009 Jaroslav Krizek, Jan 27 2010]

A157493 Apply partial sum operator thrice to sequence of squares of the first n primes.

Original entry on oeis.org

4, 21, 76, 218, 568, 1295, 2688, 5108, 9084, 15457, 25188, 39646, 60512, 89635, 129224, 182088, 251708, 341805, 456868, 601938, 782344, 1004327, 1274776, 1601612, 1994244, 2462873, 3018108, 3671398, 4434624, 5320555, 6345320
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Mathematica
    s0=s1=s2=0; Table[s0+=Prime[n]^2; s1+=s0; s2+=s1, {n,100}]
    Nest[Accumulate,Prime[Range[40]]^2,3]  (* Harvey P. Dale, Jan 27 2011 *)

A330087 Permanent of a square matrix M(n) whose general element M_{i,j} is defined by i*prime(j).

Original entry on oeis.org

1, 2, 24, 1080, 120960, 33264000, 15567552000, 12967770816000, 15768809312256000, 29377291748732928000, 85194146071325491200000, 319563241913541917491200000, 1702632952915351336393113600000, 11797543730750469409867884134400000, 99429698562764956186366527484723200000
Offset: 0

Views

Author

Stefano Spezia, Dec 01 2019

Keywords

Comments

det(M(0)) = 1, det(M(1)) = 2 and det(M(n)) = 0 for n > 1.
The trace of the matrix M(n) is A014285(n).
The antitrace of the matrix M(n) is A014148(n).
The antidiagonal of the matrix M(n) is the n-th row of the triangle A309131.

Examples

			For n = 1 the matrix M(1) is
  2
with permanent a(1) = 2.
For n = 2 the matrix M(2) is
  2, 3
  4, 6
with permanent a(2) = 24.
For n = 3 the matrix M(3) is
  2,  3,  5
  4,  6, 10
  6,  9, 15
with permanent a(3) = 1080.
		

Crossrefs

Programs

  • Maple
    with(LinearAlgebra):
    a:= n-> `if`(n=0, 1, Permanent(Matrix(n, (i, j)-> i*ithprime(j)))):
    seq(a(n), n=0..14);  # Alois P. Heinz, Dec 04 2019
  • Mathematica
    M[i_, j_, n_] := i*Prime[j]; a[n_] := If[n==0,1,Permanent[Table[M[i, j, n], {i, n}, {j, n}]]]; Array[a, 14, 0]
  • PARI
    a(n) = matpermanent(matrix(n, n, i, j, i*prime(j))); \\ Michel Marcus, Dec 04 2019

Extensions

a(0) = 1 prepended by Michel Marcus, Dec 04 2019

A356178 Numbers k such that both Sum_{i=1..k} i*prime(i) and Sum_{i=1..k} (k+1-i)*prime(i) are prime.

Original entry on oeis.org

1, 3, 199, 351, 1583, 1955, 2579, 2627, 3251, 3407, 3503, 5311, 6359, 6819, 7295, 7547, 8791, 9663, 10143, 10591, 11499, 11579, 12199, 12443, 14527, 15563, 15583, 16051, 16543, 16655, 18047, 18319, 20691, 20847, 23979, 24079, 24575, 25667, 26491, 28235, 30395, 30627, 32235, 32259, 33091, 33287, 33527
Offset: 1

Views

Author

J. M. Bergot and Robert Israel, Jul 28 2022

Keywords

Comments

Numbers k such that A014148(k) and A014285(k) are both prime.
a(n) == 3 (mod 4) for n > 1.

Examples

			a(2) = 3 is a term because Sum_{i=1..3} i*prime(i) = 1*2 + 2*3 + 3*5 = 23 and Sum_{i=1..3} (4-i)*prime(i) = 3*2 + 2*3 + 1*5 = 17 are prime.
		

Crossrefs

Programs

  • Maple
    S1:= 2: S2:= 2: S3:= 2*S2-S1: R:= 1: count:= 1: p:= 2:
    for n from 2 to 40000 do
      p:= nextprime(p);
      S1:= S1 + n*p;
      S2:= S2 + p;
      if n mod 4 = 3 and isprime(S1) then
        S3:= (n+1)*S2 - S1;
        if isprime(S3) then
           count:= count+1; R:= R, n;
        fi
      fi;
    od:
    R;
  • Mathematica
    r = Range[35000]; p = Prime[r]; Intersection[Position[Accumulate[r*p], ?PrimeQ], Position[Accumulate[Accumulate[p]], ?PrimeQ]] // Flatten (* Amiram Eldar, Jul 28 2022 *)
  • PARI
    isok(k) = my(vp=primes(k)); isprime(sum(i=1, k, i*vp[i])) && isprime(sum(i=1, k, (k+1-i)*vp[i])); \\ Michel Marcus, Jul 29 2022

A157494 Primes in A014150.

Original entry on oeis.org

2, 1429, 32869, 3189059, 5157791, 62701339, 139181423, 296686879, 522304883, 5070516751, 6276844867, 7098350179, 8983996079, 9331926623, 21211375343, 31177858939, 34861039007, 38865340309, 39918757589, 62858815181
Offset: 1

Views

Author

Keywords

Crossrefs

Programs

  • Mathematica
    s0=s1=s2=0;lst={};Do[p=Prime[n];s0+=p;s1+=s0;s2+=s1;If[PrimeQ[s2],AppendTo[lst,s2]],{n,7!}];lst
    Select[Nest[Accumulate[#]&,Prime[Range[700]],3],PrimeQ] (* Harvey P. Dale, Jul 11 2025 *)

A293210 a(n) = [x^n] (1/(1 - x)^n)*Sum_{k>=1} prime(k)*x^k.

Original entry on oeis.org

0, 2, 7, 26, 97, 366, 1388, 5288, 20225, 77618, 298766, 1153018, 4460072, 17287558, 67129566, 261095420, 1016994627, 3966529870, 15488964428, 60549061804, 236932924494, 927984726826, 3637661249946, 14270586372348, 56024073085546, 220089137078792, 865154426179408, 3402841810234762, 13391422390407194
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 02 2017

Keywords

Crossrefs

Programs

  • Mathematica
    Table[SeriesCoefficient[1/(1 - x)^n Sum[Prime[k] x^k, {k, 1, n}], {x, 0, n}], {n, 0, 28}]

Formula

a(n) = A254858(n,n).
Previous Showing 11-17 of 17 results.