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.

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A301551 Expansion of Product_{k>=1} (1 + x^k)^(sigma_7(k)).

Original entry on oeis.org

1, 1, 129, 2317, 26957, 385147, 5514889, 70250881, 866874825, 10634404922, 126906497939, 1470673175003, 16705788322140, 186487470519166, 2044203433733016, 22025647881901542, 233686866722213324, 2443978994099801452, 25211475391206919299, 256716054713570158748
Offset: 0

Views

Author

Vaclav Kotesovec, Mar 23 2018

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 30; CoefficientList[Series[Product[(1+x^k)^DivisorSigma[7, k], {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ exp(9 * Pi^(8/9) * (17*Zeta(9))^(1/9) * n^(8/9) / 2^(29/9)) * (17*Zeta(9)/Pi)^(1/18) / (3 * 2^(883/1440) * n^(5/9)).
G.f.: exp(Sum_{k>=1} sigma_8(k)*x^k/(k*(1 - x^(2*k)))). - Ilya Gutkovskiy, Oct 26 2018

A301552 Expansion of Product_{k>=1} (1 + x^k)^(sigma_8(k)).

Original entry on oeis.org

1, 1, 257, 6819, 105251, 2175749, 44995096, 796670938, 13805853214, 240569119333, 4044892975196, 65784204818948, 1051532586300939, 16521916387136217, 254423642953508270, 3848289482388789293, 57317953928614093036, 841172595390506945766, 12168324212099663732171
Offset: 0

Views

Author

Vaclav Kotesovec, Mar 23 2018

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 30; CoefficientList[Series[Product[(1+x^k)^DivisorSigma[8, k], {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ exp(5 * 2^(4/5) * Pi * (511*Zeta(9)/33)^(1/10) * n^(9/10)/9 + Pi * (11/(511*Zeta(9)))^(1/10) * n^(1/10) / (480 * 2^(4/5) * 3^(9/10))) * (511*Zeta(9)/33)^(1/20) / (2^(11/10) * sqrt(5) * n^(11/20)).
G.f.: exp(Sum_{k>=1} sigma_9(k)*x^k/(k*(1 - x^(2*k)))). - Ilya Gutkovskiy, Oct 26 2018

A356937 Number of multisets of intervals whose multiset union is of size n and covers an initial interval of positive integers.

Original entry on oeis.org

1, 1, 3, 9, 29, 94, 310, 1026, 3411, 11360, 37886, 126442, 422203, 1410189, 4711039, 15740098, 52593430, 175742438, 587266782, 1962469721, 6558071499, 21915580437, 73237274083, 244744474601, 817889464220, 2733235019732, 9133973730633, 30524096110942, 102006076541264
Offset: 0

Views

Author

Gus Wiseman, Sep 08 2022

Keywords

Comments

An interval such as {3,4,5} is a set with all differences of adjacent elements equal to 1.

Examples

			The a(1) = 1 through a(3) = 9 set multipartitions (multisets of sets):
  {{1}}  {{1,2}}    {{1,2,3}}
         {{1},{1}}  {{1},{1,2}}
         {{1},{2}}  {{1},{2,3}}
                    {{2},{1,2}}
                    {{3},{1,2}}
                    {{1},{1},{1}}
                    {{1},{1},{2}}
                    {{1},{2},{2}}
                    {{1},{2},{3}}
		

Crossrefs

A000041 counts integer partitions, strict A000009.
A000670 counts patterns, ranked by A333217, necklace A019536.
A011782 counts multisets covering an initial interval.
Intervals are counted by A000012, A001227, ranked by A073485.
Other conditions: A034691, A116540, A255906, A356933, A356942.
Other types: A107742, A356936, A356938, A356939.

Programs

  • Mathematica
    allnorm[n_]:=If[n<=0,{{}},Function[s,Array[Count[s,y_/;y<=#]+1&,n]]/@Subsets[Range[n-1]+1]];
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];
    chQ[y_]:=Or[Length[y]<=1,Union[Differences[y]]=={1}];
    Table[Length[Select[Join@@mps/@allnorm[n],And@@chQ/@#&]],{n,0,5}]
  • PARI
    EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)}
    R(n,k) = {EulerT(vector(n, j, max(0, 1+k-j)))}
    seq(n) = {my(A=1+O(y*y^n)); for(k = 1, n, A += x^k*(1 + y*Ser(R(n,k), y) - polcoef(1/(1 - x*A) + O(x^(k+2)), k+1))); Vec(subst(A,x,1))} \\ Andrew Howroyd, Jan 01 2023

Extensions

Terms a(10) and beyond from Andrew Howroyd, Jan 01 2023

A356938 Number of multisets of intervals whose multiset union is of size n and covers an initial interval of positive integers with weakly decreasing multiplicities.

Original entry on oeis.org

1, 1, 3, 7, 18, 41, 101, 228, 538, 1209
Offset: 0

Views

Author

Gus Wiseman, Sep 09 2022

Keywords

Comments

An interval such as {3,4,5} is a set of positive integers with all differences of adjacent elements equal to 1.

Examples

			The a(1) = 1 through a(4) = 18 multiset partitions:
  {{1}}  {{1,2}}    {{1,2,3}}      {{1,2,3,4}}
         {{1},{1}}  {{1},{1,2}}    {{1},{1,2,3}}
         {{1},{2}}  {{1},{2,3}}    {{1,2},{1,2}}
                    {{3},{1,2}}    {{1},{2,3,4}}
                    {{1},{1},{1}}  {{1,2},{3,4}}
                    {{1},{1},{2}}  {{4},{1,2,3}}
                    {{1},{2},{3}}  {{1},{1},{1,2}}
                                   {{1},{1},{2,3}}
                                   {{1},{2},{1,2}}
                                   {{1},{2},{3,4}}
                                   {{1},{3},{1,2}}
                                   {{1},{4},{2,3}}
                                   {{3},{4},{1,2}}
                                   {{1},{1},{1},{1}}
                                   {{1},{1},{1},{2}}
                                   {{1},{1},{2},{2}}
                                   {{1},{1},{2},{3}}
                                   {{1},{2},{3},{4}}
		

Crossrefs

A000041 counts integer partitions, strict A000009.
A000670 counts patterns, ranked by A333217, necklace A019536.
A011782 counts multisets covering an initial interval.
Intervals are counted by A000012, A001227, ranked by A073485.
Other conditions: A035310, A063834, A330783, A356934.

Programs

  • Mathematica
    strnorm[n_]:=Flatten[MapIndexed[Table[#2,{#1}]&,#]]&/@IntegerPartitions[n];
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];
    chQ[y_]:=Or[Length[y]<=1,Union[Differences[y]]=={1}];
    Table[Length[Select[Join@@mps/@strnorm[n],And@@chQ/@#&]],{n,0,5}]

A356941 Number of multiset partitions of integer partitions of n such that all blocks are gapless.

Original entry on oeis.org

1, 1, 3, 6, 13, 24, 49, 88, 166, 297, 534, 932, 1635, 2796, 4782, 8060, 13521, 22438, 37080, 60717, 98979, 160216, 258115, 413382, 659177, 1045636, 1651891, 2597849, 4069708, 6349677, 9871554, 15290322, 23604794, 36318256, 55705321, 85177643, 129865495
Offset: 0

Views

Author

Gus Wiseman, Sep 11 2022

Keywords

Comments

A multiset is gapless if it covers an interval of positive integers. For example, {2,3,3,4} is gapless but {1,1,3,3} is not.

Examples

			The a(1) = 1 through a(4) = 13 multiset partitions:
  {{1}}  {{2}}      {{3}}          {{4}}
         {{1,1}}    {{1,2}}        {{2,2}}
         {{1},{1}}  {{1,1,1}}      {{1,1,2}}
                    {{1},{2}}      {{1},{3}}
                    {{1},{1,1}}    {{2},{2}}
                    {{1},{1},{1}}  {{1,1,1,1}}
                                   {{1},{1,2}}
                                   {{2},{1,1}}
                                   {{1},{1,1,1}}
                                   {{1,1},{1,1}}
                                   {{1},{1},{2}}
                                   {{1},{1},{1,1}}
                                   {{1},{1},{1},{1}}
		

Crossrefs

A000041 counts integer partitions, strict A000009.
A000670 counts patterns, ranked by A333217, necklace A019536.
A001055 counts factorizations.
A011782 counts multisets covering an initial interval.
A356069 counts gapless divisors, initial A356224 (complement A356225).
Gapless multisets are counted by A034296, ranked by A073491.
Other types: A356233, A356942, A356943, A356944.
Other conditions: A001970, A006171, A007294, A089259, A107742, A356932.

Programs

  • Mathematica
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]];
    nogapQ[m_]:=Or[m=={},Union[m]==Range[Min[m],Max[m]]];
    Table[Length[Select[Join@@mps/@IntegerPartitions[n],And@@nogapQ/@#&]],{n,0,5}]
  • PARI
    \\ Here G(n) gives A034296 as vector
    G(N) = Vec(sum(n=1, N, x^n/(1-x^n) * prod(k=1, n-1, 1+x^k+O(x*x^(N-n))) ));
    seq(n) = {my(u=G(n)); Vec(1/prod(k=1, n-1, (1 - x^k + O(x*x^n))^u[k])) } \\ Andrew Howroyd, Dec 30 2022

Formula

G.f.: 1/Product_{k>=1} (1 - x^k)^A034296(k). - Andrew Howroyd, Dec 30 2022

Extensions

Terms a(11) and beyond from Andrew Howroyd, Dec 30 2022

A318416 Expansion of Product_{i>=1, j>=1} (1 + i*j*x^(i*j)).

Original entry on oeis.org

1, 1, 4, 10, 22, 50, 115, 231, 470, 995, 1912, 3745, 7222, 13608, 25345, 47322, 85654, 155163, 278867, 494080, 870618, 1524769, 2640527, 4549564, 7802037, 13251684, 22412317, 37706268, 63015263, 104800015, 173574936, 285694401, 468449681, 764775169, 1242535747, 2010866469, 3242127656
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 26 2018

Keywords

Crossrefs

Programs

  • Maple
    a:=series(mul(mul(1+i*j*x^(i*j),j=1..55),i=1..55),x=0,37): seq(coeff(a,x,n),n=0..36); # Paolo P. Lava, Apr 02 2019
  • Mathematica
    nmax = 36; CoefficientList[Series[Product[Product[(1 + i j x^(i j)), {i, 1, nmax}], {j, 1, nmax}], {x, 0, nmax}], x]
    nmax = 36; CoefficientList[Series[Product[(1 + k x^k)^DivisorSigma[0, k], {k, 1, nmax}], {x, 0, nmax}], x]
    nmax = 36; CoefficientList[Series[Exp[Sum[Sum[(-d)^(k/d + 1) DivisorSigma[0, d], {d, Divisors[k]}] x^k/k, {k, 1, nmax}]], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-d)^(k/d + 1) DivisorSigma[0, d], {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 36}]
    nmax = 36; s = 1 + x; Do[s *= Sum[Binomial[DivisorSigma[0, k], j]*k^j*x^(j*k), {j, 0, nmax/k}]; s = Expand[s]; s = Take[s, Min[nmax + 1, Exponent[s, x] + 1, Length[s]]];, {k, 2, nmax}]; CoefficientList[s, x] (* Vaclav Kotesovec, Aug 27 2018 *)

Formula

G.f.: Product_{k>=1} (1 + k*x^k)^tau(k), where tau = number of divisors (A000005).
G.f.: exp(Sum_{k>=1} ( Sum_{d|k} (-d)^(k/d+1)*tau(d) ) * x^k/k).

A318696 Expansion of e.g.f. Product_{i>=1, j>=1} (1 + x^(i*j))^(1/(i*j)).

Original entry on oeis.org

1, 1, 2, 10, 34, 218, 1708, 12556, 97340, 1139932, 12602584, 142757624, 1983086488, 26745019000, 402951386576, 7181178238672, 115410887636752, 2039658743085584, 42354537803172640, 815690033731561888, 17593347085888752416, 416765224159172991136, 9379433694333768563392
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 31 2018

Keywords

Crossrefs

Programs

  • Maple
    seq(n!*coeff(series(mul((1+x^k)^(tau(k)/k),k=1..100),x=0,23),x,n),n=0..22); # Paolo P. Lava, Jan 09 2019
  • Mathematica
    nmax = 22; CoefficientList[Series[Product[Product[(1 + x^(i j))^(1/(i j)), {i, 1, nmax}], {j, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    nmax = 22; CoefficientList[Series[Product[(1 + x^k)^(DivisorSigma[0, k]/k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
    nmax = 22; CoefficientList[Series[Exp[Sum[Sum[(-1)^(k/d + 1) DivisorSigma[0, d], {d, Divisors[k]}] x^k/k, {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[(-1)^(k/d + 1) DivisorSigma[0, d], {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[n! a[n], {n, 0, 22}]
    nmax = 22; s = 1 + x; Do[s *= Sum[Binomial[DivisorSigma[0, k]/k, j]*x^(j*k), {j, 0, nmax/k}]; s = Expand[s]; s = Take[s, Min[nmax + 1, Exponent[s, x] + 1, Length[s]]];, {k, 2, nmax}]; Take[CoefficientList[s, x], nmax + 1] * Range[0, nmax]! (* Vaclav Kotesovec, Sep 01 2018 *)

Formula

E.g.f.: Product_{k>=1} (1 + x^k)^(tau(k)/k), where tau = number of divisors (A000005).
E.g.f.: exp(Sum_{k>=1} ( Sum_{d|k} (-1)^(k/d+1)*tau(d) ) * x^k/k).

A356936 Number of multiset partitions of the multiset of prime indices of n into intervals. Number of factorizations of n into members of A073485.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 2, 3, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 1, 2, 1, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1
Offset: 1

Views

Author

Gus Wiseman, Sep 08 2022

Keywords

Comments

An interval is a set of positive integers with all differences of adjacent elements equal to 1.
A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.

Examples

			The a(n) multiset partitions for n = 6, 30, 36, 90, 180:
  {12}    {123}      {12}{12}      {12}{23}      {12}{123}
  {1}{2}  {1}{23}    {1}{2}{12}    {2}{123}      {1}{12}{23}
          {3}{12}    {1}{1}{2}{2}  {1}{2}{23}    {1}{2}{123}
          {1}{2}{3}                {2}{3}{12}    {3}{12}{12}
                                   {1}{2}{2}{3}  {1}{1}{2}{23}
                                                 {1}{2}{3}{12}
                                                 {1}{1}{2}{2}{3}
The a(n) factorizations for n = 6, 30, 36, 90, 180:
  (6)    (30)     (6*6)      (3*30)     (6*30)
  (2*3)  (5*6)    (2*3*6)    (6*15)     (5*6*6)
         (2*15)   (2*2*3*3)  (3*5*6)    (2*3*30)
         (2*3*5)             (2*3*15)   (2*6*15)
                             (2*3*3*5)  (2*3*5*6)
                                        (2*2*3*15)
                                        (2*2*3*3*5)
		

Crossrefs

A000688 counts factorizations into prime powers.
A001055 counts factorizations.
A001221 counts prime divisors, sum A001414.
A001222 counts prime factors with multiplicity.
A356069 counts gapless divisors, initial A356224 (complement A356225).
A056239 adds up prime indices, row sums of A112798.
Intervals are counted by A000012, A001227, ranked by A073485.
Other conditions: A050320, A050330, A322585, A356931, A356945.

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];
    chQ[y_]:=Or[Length[y]<=1,Union[Differences[y]]=={1}];
    Table[Length[Select[facs[n],And@@chQ/@primeMS/@#&]],{n,100}]

A356945 Number of multiset partitions of the prime indices of n such that each block covers an initial interval. Number of factorizations of n into members of A055932.

Original entry on oeis.org

1, 1, 0, 2, 0, 1, 0, 3, 0, 0, 0, 2, 0, 0, 0, 5, 0, 1, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 1, 0, 7, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 11, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 1

Views

Author

Gus Wiseman, Sep 08 2022

Keywords

Comments

A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.

Examples

			The a{n} multiset partitions for n = 8, 24, 72, 96:
  {{111}}      {{1112}}      {{11122}}      {{111112}}
  {{1}{11}}    {{1}{112}}    {{1}{1122}}    {{1}{11112}}
  {{1}{1}{1}}  {{11}{12}}    {{11}{122}}    {{11}{1112}}
               {{1}{1}{12}}  {{12}{112}}    {{111}{112}}
                             {{1}{1}{122}}  {{12}{1111}}
                             {{1}{12}{12}}  {{1}{1}{1112}}
                                            {{1}{11}{112}}
                                            {{11}{11}{12}}
                                            {{1}{12}{111}}
                                            {{1}{1}{1}{112}}
                                            {{1}{1}{11}{12}}
                                            {{1}{1}{1}{1}{12}}
		

Crossrefs

Positions of 0's are A080259, complement A055932.
A000688 counts factorizations into prime powers.
A001055 counts factorizations.
A001221 counts prime divisors, with sum A001414.
A001222 counts prime factors with multiplicity.
A056239 adds up prime indices, row sums of A112798.
A356069 counts gapless divisors, initial A356224 (complement A356225).
Multisets covering an initial interval are counted by A000009, A000041, A011782, ranked by A055932.
Other types: A034691, A089259, A356954, A356955.
Other conditions: A050320, A050330, A322585, A356233, A356931, A356936.

Programs

  • Mathematica
    facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];
    nnQ[m_]:=PrimePi/@First/@FactorInteger[m]==Range[PrimePi[Max@@First/@FactorInteger[m]]];
    Table[Length[Select[facs[n],And@@nnQ/@#&]],{n,100}]

A280664 G.f.: Product_{k>=1, j>=1} (1 + x^(j*k^4)).

Original entry on oeis.org

1, 1, 1, 2, 2, 3, 4, 5, 6, 8, 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 66, 79, 93, 109, 128, 150, 175, 204, 237, 274, 318, 367, 423, 487, 559, 641, 734, 839, 957, 1091, 1241, 1410, 1601, 1814, 2053, 2322, 2622, 2957, 3334, 3752, 4218, 4740, 5318, 5962, 6679
Offset: 0

Views

Author

Vaclav Kotesovec, Jan 07 2017

Keywords

Comments

In general, if m>=3 and g.f. = Product_{k>=1, j>=1} (1+x^(j*k^m)), then a(n, m) ~ exp(Pi*sqrt(Zeta(m)*n/3) + (2^(1/m)-1) * Pi^(-1/m) * Gamma(1+1/m) * Zeta(1+1/m) * Zeta(1/m) * (3*n/Zeta(m))^(1/(2*m))) * Zeta(m)^(1/4) / (2^(5/4) * 3^(1/4) * n^(3/4)).

Crossrefs

Cf. A107742 (m=1), A280451 (m=2), A280663 (m=3).
Cf. A280662.

Programs

  • Mathematica
    nmax = 100; CoefficientList[Series[Product[1+x^(j*k^4), {k, 1, Floor[nmax^(1/4)]+1}, {j, 1, Floor[nmax/k^4]+1}], {x, 0, nmax}], x]

Formula

a(n) ~ exp(Pi^3 * sqrt(n/30)/3 + 2^(-15/8) * 3^(3/8) * 5^(1/8) * (2^(1/4)-1) * Pi^(-3/4) * Gamma(1/4) * Zeta(5/4) * Zeta(1/4) * n^(1/8)) * Pi / (2^(3/2) * 3^(3/4) * 5^(1/4) * n^(3/4)).
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