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 1-10 of 12 results. Next

A117278 Triangle read by rows: T(n,k) is the number of partitions of n into k prime parts (n>=2, 1<=k<=floor(n/2)).

Original entry on oeis.org

1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 2, 1, 0, 2, 1, 1, 1, 1, 0, 2, 2, 1, 0, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 1, 0, 2, 1, 3, 2, 1, 1, 0, 1, 3, 2, 3, 2, 1, 0, 2, 2, 3, 3, 2, 1, 1, 1, 0, 4, 3, 3, 3, 2, 1, 0, 2, 2, 4, 3, 4, 2, 1, 1, 1, 1, 3, 4, 5, 3, 3, 2, 1, 0, 2, 2, 6, 4, 4, 4, 2, 1, 1, 0, 1, 5, 3, 6
Offset: 2

Views

Author

Emeric Deutsch, Mar 07 2006

Keywords

Comments

Row n has floor(n/2) terms. Row sums yield A000607. T(n,1) = A010051(n) (the characteristic function of the primes). T(n,2) = A061358(n). Sum(k*T(n,k), k>=1) = A084993(n).

Examples

			T(12,3) = 2 because we have [7,3,2] and [5,5,2].
Triangle starts:
  1;
  1;
  0, 1;
  1, 1;
  0, 1, 1;
  1, 1, 1;
  0, 1, 1, 1;
  0, 1, 2, 1;
  ...
		

Crossrefs

Row sums give A000607.
T(A000040(n),n) gives A259254(n).

Programs

  • Maple
    g:=1/product(1-t*x^(ithprime(j)),j=1..30): gser:=simplify(series(g,x=0,30)): for n from 2 to 22 do P[n]:=sort(coeff(gser,x^n)) od: for n from 2 to 22 do seq(coeff(P[n],t^j),j=1..floor(n/2)) od; # yields sequence in triangular form
    # second Maple program:
    b:= proc(n, i) option remember;
          `if`(n=0, [1], `if`(i<1, [], zip((x, y)->x+y, b(n, i-1),
           [0, `if`(ithprime(i)>n, [], b(n-ithprime(i), i))[]], 0)))
        end:
    T:= n-> subsop(1=NULL, b(n, numtheory[pi](n)))[]:
    seq(T(n), n=2..25);  # Alois P. Heinz, Nov 16 2012
  • Mathematica
    (* As triangle: *) nn=20;a=Product[1/(1-y x^i),{i,Table[Prime[n],{n,1,nn}]}];Drop[CoefficientList[Series[a,{x,0,nn}],{x,y}],2,1]//Grid (* Geoffrey Critzer, Oct 30 2012 *)
  • PARI
    parts(n, pred)={prod(k=1, n, if(pred(k), 1/(1-y*x^k) + O(x*x^n), 1))}
    {my(n=15); apply(p->Vecrev(p/y), Vec(parts(n, isprime)-1))} \\ Andrew Howroyd, Dec 28 2017

Formula

G.f.: G(t,x) = -1+1/product(1-tx^(p(j)), j=1..infinity), where p(j) is the j-th prime.

A024938 Total number of parts in all partitions of n into distinct prime parts.

Original entry on oeis.org

0, 1, 1, 0, 3, 0, 3, 2, 2, 5, 1, 5, 3, 5, 5, 7, 5, 10, 6, 10, 12, 10, 15, 12, 16, 17, 17, 19, 22, 17, 27, 21, 30, 30, 31, 35, 36, 40, 45, 45, 49, 53, 50, 62, 60, 69, 69, 73, 78, 85, 88, 98, 100, 105, 116, 116, 134, 135, 141, 149, 154, 168, 176, 188, 195, 206, 211, 232, 242, 255, 267, 276
Offset: 1

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Author

Keywords

Examples

			a(16) = 7 because the partitions of 16 into distinct prime parts are [13,3], [11,5] and [11,3,2].
		

Crossrefs

Cf. A084993.

Programs

  • Maple
    g:=sum(x^ithprime(j)/(1+x^ithprime(j)),j=1..30)*product(1+x^ithprime(j),j=1..30): gser:=series(g,x=0,80): seq(coeff(gser,x,n),n=1..75); # Emeric Deutsch, Apr 01 2006
    # second Maple program:
    with(numtheory):
    b:= proc(n, i) option remember; local g;
          if n=0 then [1, 0]
        elif i<1 then [0, 0]
        else g:= `if`(ithprime(i)>n, [0$2], b(n-ithprime(i), i-1));
             b(n, i-1) +g +[0, g[1]]
          fi
        end:
    a:= n-> b(n, pi(n))[2]:
    seq(a(n), n=1..80);  # Alois P. Heinz, Oct 30 2012
  • Mathematica
    Rest@ CoefficientList[ Series[ Sum[x^Prime@j/(1 + x^Prime@j), {j, 20}]* Product[1 + x^Prime@j, {j, 20}], {x, 0, 70}], x] (* Robert G. Wilson v *)
    b[n_, i_] := b[n, i] = Module[{g}, If[n==0, {1, 0}, If[i < 1, {0, 0}, g = If[ Prime[i] > n, {0, 0}, b[n - Prime[i], i-1]]; b[n, i-1] + g + {0, g[[1]]}]]]; a[n_] := b[n, PrimePi[n]][[2]]; Table[a[n], {n, 1, 80}] (* Jean-François Alcover, Dec 27 2015, after Alois P. Heinz *)
  • PARI
    sumparts(n, pred)={sum(k=1, n, 1 - 1/(1+pred(k)*x^k) + O(x*x^n))*prod(k=1, n, 1+pred(k)*x^k + O(x*x^n))}
    {my(n=60); Vec(sumparts(n, isprime), -n)} \\ Andrew Howroyd, Dec 28 2017

Formula

G.f.: sum(x^p(j)/(1+x^p(j)),j>=1)*product(1+x^p(j), j>=1), where p(j) is the j-th prime. - Vladeta Jovovic, Jul 17 2003

Extensions

More terms from Vladeta Jovovic, Jul 17 2003

A281544 Expansion of Sum_{k>=2} x^prime(k)/(1 - x^prime(k)) / Product_{k>=2} (1 - x^prime(k)).

Original entry on oeis.org

0, 0, 1, 0, 1, 2, 1, 2, 3, 4, 4, 6, 7, 8, 11, 12, 15, 18, 20, 26, 29, 34, 40, 46, 54, 62, 71, 82, 94, 106, 122, 138, 157, 178, 201, 226, 254, 286, 321, 360, 402, 448, 501, 558, 619, 690, 764, 846, 938, 1036, 1145, 1264, 1392, 1532, 1687, 1854, 2036, 2234, 2448, 2680, 2934, 3210, 3507, 3828, 4178, 4554, 4961, 5404
Offset: 1

Views

Author

Ilya Gutkovskiy, Jan 23 2017

Keywords

Comments

Total number of parts in all partitions of n into odd primes.
Convolution of A005087 and A099773.

Examples

			a(14) = 8 because we have [11, 3], [7, 7], [5, 3, 3, 3] and 2 + 2 + 4 = 8.
		

Crossrefs

Programs

  • Mathematica
    nmax = 68; Rest[CoefficientList[Series[Sum[x^Prime[k]/(1 - x^Prime[k]), {k, 2, nmax}]/Product[1 - x^Prime[k], {k, 2, nmax}], {x, 0, nmax}], x]]
  • PARI
    sumparts(n, pred)={sum(k=1, n, 1/(1-pred(k)*x^k) - 1 + O(x*x^n))/prod(k=1, n, 1-pred(k)*x^k + O(x*x^n))}
    {my(n=60); Vec(sumparts(n, v->v>2 && isprime(v)), -n)} \\ Andrew Howroyd, Dec 28 2017

Formula

G.f.: Sum_{k>=2} x^prime(k)/(1 - x^prime(k)) / Product_{k>=2} (1 - x^prime(k)).

A281617 Expansion of Sum_{i = p*q, p prime, q prime} x^i/(1 - x^i) / Product_{j = p*q, p prime, q prime} (1 - x^j).

Original entry on oeis.org

0, 0, 0, 0, 1, 0, 1, 0, 2, 1, 3, 0, 5, 2, 6, 3, 9, 3, 14, 7, 16, 10, 23, 12, 32, 20, 37, 28, 52, 35, 69, 49, 80, 68, 110, 83, 137, 112, 166, 150, 215, 178, 268, 239, 324, 303, 406, 365, 504, 472, 604, 584, 747, 708, 917, 888, 1089, 1085, 1337, 1311, 1618, 1606, 1916, 1954, 2332, 2334, 2782, 2829, 3300, 3407, 3963
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 25 2017

Keywords

Comments

Total number of parts in all partitions of n into semiprimes (A001358).
Convolution of A086971 and A101048.

Examples

			a(12) = 5 because we have [6, 6], [4, 4, 4] and 2 + 3 = 5.
		

Crossrefs

Programs

  • Maple
    h:= proc(n) option remember; `if`(n=0, 0,
         `if`(numtheory[bigomega](n)=2, n, h(n-1)))
        end:
    b:= proc(n, i) option remember; `if`(n=0, [1, 0], `if`(i<1, [0$2],
         `if`(i>n, 0, (p-> p+[0, p[1]])(b(n-i, h(min(n-i, i)))))+b(n, h(i-1))))
        end:
    a:= n-> b(n, h(n))[2]:
    seq(a(n), n=0..70);  # Alois P. Heinz, May 19 2021
  • Mathematica
    nmax = 70; Rest[CoefficientList[Series[Sum[Floor[PrimeOmega[i]/2] Floor[2/PrimeOmega[i]] x^i/(1 - x^i), {i, 2, nmax}]/Product[1 - Floor[PrimeOmega[j]/2] Floor[2/PrimeOmega[j]] x^j, {j, 2, nmax}], {x, 0, nmax}], x]]

Formula

G.f.: Sum_{i = p*q, p prime, q prime} x^i/(1 - x^i) / Product_{j = p*q, p prime, q prime} (1 - x^j).
a(n) = Sum_{k>0} k * A344447(n,k). - Alois P. Heinz, May 19 2021

A284827 Expansion of Sum_{i>=1} x^prime(i)/(1 - x^prime(i)) * Product_{j>=i} 1/(1 - x^prime(j)).

Original entry on oeis.org

0, 1, 1, 2, 2, 5, 4, 6, 9, 11, 13, 18, 20, 26, 34, 37, 47, 55, 66, 80, 96, 111, 130, 150, 180, 206, 240, 278, 318, 366, 419, 483, 549, 626, 716, 803, 913, 1034, 1167, 1314, 1477, 1659, 1861, 2085, 2332, 2605, 2902, 3232, 3602, 3999, 4442, 4930, 5454, 6034, 6675, 7375, 8133, 8967, 9870, 10855
Offset: 1

Views

Author

Ilya Gutkovskiy, Apr 03 2017

Keywords

Comments

Total number of smallest parts in all partitions of n into prime parts.

Examples

			a(10) = 11 because we have [7, 3], [5, 5], [5, 3, 2], [3, 3, 2, 2], [2, 2, 2, 2, 2] and 1 + 2 + 1 + 2 + 5 = 11.
		

Crossrefs

Programs

  • Mathematica
    nmax = 60; Rest[CoefficientList[Series[Sum[x^Prime[i]/(1 - x^Prime[i]) Product[1/(1 - x^Prime[j]), {j, i, nmax}], {i, 1, nmax}], {x, 0, nmax}], x]]

Formula

G.f.: Sum_{i>=1} x^prime(i)/(1 - x^prime(i)) * Product_{j>=i} 1/(1 - x^prime(j)).

A284828 Expansion of Sum_{i>=2} x^prime(i)/(1 - x^prime(i)) * Product_{j>=i} 1/(1 - x^prime(j)).

Original entry on oeis.org

0, 0, 1, 0, 1, 2, 1, 1, 3, 3, 3, 5, 4, 6, 9, 7, 10, 11, 12, 17, 19, 22, 23, 26, 33, 36, 41, 48, 52, 59, 66, 78, 85, 97, 112, 117, 134, 151, 169, 187, 207, 230, 255, 284, 313, 348, 379, 418, 465, 508, 561, 620, 674, 737, 812, 892, 972, 1064, 1157, 1257, 1379, 1503, 1639, 1776, 1935, 2101, 2279, 2483
Offset: 1

Views

Author

Ilya Gutkovskiy, Apr 03 2017

Keywords

Comments

Total number of smallest parts in all partitions of n into odd prime parts (A065091).

Examples

			a(16) = 7 because we have [13, 3], [11, 5], [7, 3, 3, 3], [5, 5, 3, 3] and 1 + 1 + 3 + 2 = 7.
		

Crossrefs

Programs

  • Mathematica
    nmax = 68; Rest[CoefficientList[Series[Sum[x^Prime[i]/(1 - x^Prime[i]) Product[1/(1 - x^Prime[j]), {j, i, nmax}], {i, 2, nmax}], {x, 0, nmax}], x]]
  • PARI
    x = 'x + O('x ^ 70); concat([0, 0], Vec(sum(i=2, 70, x^prime(i)/(1 - x^prime(i)) * prod(j=i, 70, 1/(1 - x^prime(j)))))) \\ Indranil Ghosh, Apr 05 2017

Formula

G.f.: Sum_{i>=2} x^prime(i)/(1 - x^prime(i)) * Product_{j>=i} 1/(1 - x^prime(j)).

A276560 Expansion of Sum_{k>=1} prime(k)*x^prime(k)/(1 - x^prime(k)) * Product_{k>=1} 1/(1 - x^prime(k)).

Original entry on oeis.org

0, 2, 3, 4, 10, 12, 21, 24, 36, 50, 66, 84, 117, 140, 180, 224, 289, 342, 437, 520, 630, 770, 920, 1104, 1300, 1560, 1809, 2156, 2523, 2940, 3441, 3968, 4620, 5338, 6125, 7092, 8103, 9272, 10608, 12080, 13776, 15624, 17759, 20064, 22680, 25622, 28858, 32496, 36456, 40950, 45849, 51324, 57399, 64044, 71390
Offset: 1

Views

Author

Ilya Gutkovskiy, Apr 10 2017

Keywords

Comments

Sum of all parts of all partitions of n into prime parts.
Convolution of the sequences A000607 and A008472.

Examples

			a(6) = 12 because we have [3, 3], [2, 2, 2] and 2*6 = 12.
		

Crossrefs

Programs

  • Mathematica
    nmax = 55; Rest[CoefficientList[Series[Sum[Prime[k] x^Prime[k]/(1 - x^Prime[k]), {k, 1, nmax}] Product[1/(1 - x^Prime[k]), {k, 1, nmax}], {x, 0, nmax}], x]]
    nmax = 55; Rest[CoefficientList[Series[x D[Product[1/(1 - x^Prime[k]), {k, 1, nmax}], x], {x, 0, nmax}], x]]
    Table[Total@Flatten[IntegerPartitions[n,All,Prime@Range@PrimePi@n]],{n,52}] (* Giorgos Kalogeropoulos, Sep 12 2021 *)

Formula

G.f.: Sum_{k>=1} prime(k)*x^prime(k)/(1 - x^prime(k)) * Product_{k>=1} 1/(1 - x^prime(k)).
G.f.: x*f'(x), where f(x) = Product_{k>=1} 1/(1 - x^prime(k)).
a(n) = n*A000607(n).
a(n) ~ n*exp(2*Pi*sqrt(n/log(n))/sqrt(3)).

A281449 Expansion of Sum_{k>=1} x^(prime(k)^2)/(1 - x^(prime(k)^2)) / Product_{k>=1} (1 - x^(prime(k)^2)).

Original entry on oeis.org

0, 0, 0, 1, 0, 0, 0, 2, 1, 0, 0, 3, 2, 0, 0, 4, 3, 2, 0, 5, 4, 3, 0, 6, 6, 4, 3, 7, 8, 5, 4, 8, 10, 8, 5, 13, 12, 10, 6, 15, 14, 12, 10, 17, 21, 14, 12, 19, 25, 18, 14, 25, 29, 27, 16, 28, 33, 33, 21, 31, 42, 38, 31, 34, 47, 43, 38, 41, 52, 54, 43, 53, 57, 62, 51, 62, 67, 69, 64, 68, 82, 76, 74, 78, 94, 89, 82, 93
Offset: 1

Views

Author

Ilya Gutkovskiy, Jan 27 2017

Keywords

Comments

Total number of parts in all partitions of n into squares of primes (A001248).
Convolution of A056170 and A090677.

Examples

			a(25) = 6 because we have [25], [9, 4, 4, 4, 4] and 1 + 5 = 6.
		

Crossrefs

Programs

  • Mathematica
    nmax = 88; Rest[CoefficientList[Series[Sum[x^Prime[k]^2/(1 - x^Prime[k]^2), {k, 1, nmax}]/Product[1 - x^Prime[k]^2, {k, 1, nmax}], {x, 0, nmax}], x]]

Formula

G.f.: Sum_{k>=1} x^(prime(k)^2)/(1 - x^(prime(k)^2)) / Product_{k>=1} (1 - x^(prime(k)^2)).

A281616 Expansion of Sum_{p prime, i>=1} x^(p^i)/(1 - x^(p^i)) / Product_{p prime, j>=1} (1 - x^(p^j)).

Original entry on oeis.org

0, 1, 1, 3, 3, 7, 8, 15, 18, 28, 36, 53, 66, 91, 117, 156, 195, 254, 318, 407, 503, 630, 777, 965, 1176, 1439, 1750, 2124, 2559, 3078, 3692, 4417, 5257, 6246, 7405, 8753, 10314, 12127, 14233, 16668, 19464, 22687, 26406, 30662, 35539, 41109, 47495, 54767, 63044, 72454, 83167, 95305, 109054, 124607, 142209, 162076, 184464
Offset: 1

Views

Author

Ilya Gutkovskiy, Jan 25 2017

Keywords

Comments

Total number of parts in all partitions of n into prime power parts (1 excluded).
Convolution of A001222 and A023894.

Examples

			a(9) = 18 because we have [9], [7, 2], [5, 4], [5, 2, 2], [4, 3, 2], [3, 3, 3], [3, 2, 2, 2] and 1 + 2 + 2 + 3 + 3 + 3 + 4 = 18.
		

Crossrefs

Programs

  • Mathematica
    nmax = 57; Rest[CoefficientList[Series[Sum[Floor[1/PrimeNu[i]] x^i/(1 - x^i), {i, 2, nmax}]/Product[1 - Floor[1/PrimeNu[j]] x^j, {j, 2, nmax}], {x, 0, nmax}], x]]

Formula

G.f.: Sum_{p prime, i>=1} x^(p^i)/(1 - x^(p^i)) / Product_{p prime, j>=1} (1 - x^(p^j)).

A186409 Total number of parts in all partitions of prime(n).

Original entry on oeis.org

3, 6, 20, 54, 275, 556, 1965, 3498, 10206, 43453, 68135, 242812, 536104, 785437, 1644136, 4712040, 12760906, 17591088, 44736332, 81493581, 109311863, 257863391, 448980978, 1007135164, 2840344772, 4695605081, 6015397025, 9803584533, 12473509636, 20063812526
Offset: 1

Views

Author

Omar E. Pol, Aug 11 2011

Keywords

Examples

			For n = 3 the third prime number is 5; the partitions of 5 are [5], [4, 1], [3, 2], [3, 1, 1], [2, 2, 1], [2, 1, 1, 1], [1, 1, 1, 1, 1]; there are 20 parts, so a(3) = 20.
		

Crossrefs

Formula

a(n) = A006128(A000040(n)) = A006128(prime(n)).
Showing 1-10 of 12 results. Next