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 16 results. Next

A299757 Weight of the strict integer partition with FDH number n.

Original entry on oeis.org

0, 1, 2, 3, 4, 3, 5, 4, 6, 5, 7, 5, 8, 6, 6, 9, 10, 7, 11, 7, 7, 8, 12, 6, 13, 9, 8, 8, 14, 7, 15, 10, 9, 11, 9, 9, 16, 12, 10, 8, 17, 8, 18, 10, 10, 13, 19, 11, 20, 14, 12, 11, 21, 9, 11, 9, 13, 15, 22, 9, 23, 16, 11, 12, 12, 10, 24, 13, 14, 10, 25, 10, 26, 17
Offset: 1

Views

Author

Gus Wiseman, Feb 18 2018

Keywords

Comments

Let f(n) = A050376(n) be the n-th Fermi-Dirac prime. Every positive integer n has a unique factorization of the form n = f(s_1)*...*f(s_k) where the s_i are strictly increasing positive integers. This determines a unique strict integer partition (s_k...s_1) whose FDH number is then defined to be n.
In analogy with the Heinz number correspondence between integer partitions and positive integers (see A056239), FDH numbers give a correspondence between strict integer partitions and positive integers.

Examples

			Sequence of strict integer partitions begins: () (1) (2) (3) (4) (2,1) (5) (3,1) (6) (4,1) (7) (3,2) (8) (5,1) (4,2) (9).
		

Crossrefs

Programs

  • Mathematica
    FDfactor[n_]:=If[n===1,{},Sort[Join@@Cases[FactorInteger[n],{p_,k_}:>Power[p,Cases[Position[IntegerDigits[k,2]//Reverse,1],{m_}->2^(m-1)]]]]];
    nn=200;FDprimeList=Array[FDfactor,nn,1,Union];
    FDrules=MapIndexed[(#1->#2[[1]])&,FDprimeList];
    Table[Total[FDfactor[n]/.FDrules],{n,nn}]

A061773 Triangle in which n-th row lists Matula-Goebel numbers for all rooted trees with n nodes.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 19, 15, 18, 20, 21, 22, 23, 24, 26, 28, 29, 31, 32, 34, 37, 38, 41, 43, 53, 59, 67, 25, 27, 30, 33, 35, 36, 39, 40, 42, 44, 46, 47, 48, 49, 51, 52, 56, 57, 58, 61, 62, 64, 68, 71, 73, 74, 76, 79, 82, 83, 86, 89, 101, 106
Offset: 1

Views

Author

N. J. A. Sloane, Jun 22 2001

Keywords

Comments

Let p(1)=2, ... denote the primes. The label f(T) for a rooted tree T is 1 if T has 1 node, otherwise f(T) = Product p(f(T_i)) where the T_i are the subtrees obtained by deleting the root and the edges adjacent to it.
n-th row has A000081(n) terms.
First entry in row n is A005517(n).
Last entry in row n is A005518(n).
The Maple program yields row n after defining F = A005517(n) and L = A005518(n).

Examples

			The labels for the rooted trees with at most 4 nodes are as follows (x is the root):
                                         o
                                         |
               o         o        o   o  o
               |          \        \ /   |
     o  o   o  o  o o o    o   o    o    o
     |   \ /   |   \|/      \ /     |    |
  x  x    x    x    x        x      x    x
  1  2    4    3    8        6      7    5 (label)
Triangle begins:
1;
2;
3,4;
5,6,7,8;
9,10,11,12,13,14,16,17,19;
15,18,20,21,22,23,24,26,28,29,31,32,34,37,38,41,43,53,59,67;
25,27,30,33,35,36,39,40,42,44,46,47,48,49,51,52,56,57,58,61,62,64,68,\
71,73,74,76,79,82,83,86,89,101,106,107,109,118,127,131,134,139,157,163,\
179,191,241,277,331;
...
Triangle of rooted trees represented as finitary multisets begins:
(),
(()),
((())), (()()),
(((()))), (()(())), ((()())), (()()()),
((())(())), (()((()))), ((((())))), (()()(())), ((()(()))), (()(()())), (()()()()), (((()()))), ((()()())). - _Gus Wiseman_, Dec 21 2016
		

Crossrefs

Cf. A061775 (number of nodes), A000081 (row lengths), A005517 (row minimum), A005518 (row maximum), A214572 (row n=8).
Cf. A347620 (inverse permutation).

Programs

  • Maple
    n := 8: F := 45: L := 2221: with(numtheory): N := proc (m) local r, s: r := proc (m) options operator, arrow: op(1, factorset(m)) end proc: s := proc (m) options operator, arrow: m/r(m) end proc: if m = 1 then 1 elif bigomega(m) = 1 then 1+N(pi(m)) else N(r(m))+N(s(m))-1 end if end proc: A := {}: for k from F to L do if N(k) = n then A := `union`(A, {k}) else  end if end do: A;
  • Mathematica
    F[n_] := F[n] = Which[n == 1, 1, n == 2, 2, Mod[n, 3] == 0, 3*5^(n/3-1), Mod[n, 3] == 1, 5^(n/3-1/3), True, 9*5^(n/3-5/3)]; L[n_] := L[n] = Switch[n, 1, 1, 2, 2, 3, 4, 4, 8, , Prime[L[n-1]]]; r[m] := FactorInteger[m][[1, 1]]; s[m_] := m/r[m]; NN[m_] := NN[m] = Which[m == 1, 1, PrimeOmega[m] == 1, 1+NN[PrimePi[m]], True, NN[r[m]]+NN[s[m]]-1]; row[n_] := Module[{A, k}, A = {}; For[k = F[n], k <= L[n], k++, If[NN[k] == n, A = Union[A, {k}]]]; A]; Table[row[n], {n, 1, 8}] // Flatten (* Jean-François Alcover, Mar 06 2014, after Maple *)
    nn=8;MGweight[n_]:=If[n===1,1,1+Total[Cases[FactorInteger[n],{p_,k_}:>k*MGweight[PrimePi[p]]]]];
    Take[GatherBy[Range[Switch[nn,1,1,2,2,3,4,,Nest[Prime,8,nn-4]]],MGweight],nn] (* _Gus Wiseman, Dec 21 2016 *)
  • PARI
    \\ See links.

Extensions

More terms from Emeric Deutsch, May 01 2004

A279861 Number of transitive finitary sets with n brackets. Number of transitive rooted identity trees with n nodes.

Original entry on oeis.org

1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 2, 1, 2, 2, 2, 5, 4, 6, 8, 10, 14, 23, 26, 34, 46, 64, 81, 115, 158, 199, 277, 376, 505, 684, 934, 1241, 1711, 2300, 3123, 4236, 5763, 7814, 10647, 14456, 19662
Offset: 1

Views

Author

Gus Wiseman, Dec 21 2016

Keywords

Comments

A finitary set is transitive if every element is also a subset. Transitive sets are also called full sets.

Examples

			Sequence of transitive finitary sets begins:
1  ()
2  (())
4  (()(()))
7  (()(())((())))
8  (()(())(()(())))
11 (()(())((()))(((()))))
   (()(())((()))(()(())))
12 (()(())((()))(()((()))))
13 (()(())((()))((())((()))))
   (()(())(()(()))((()(()))))
14 (()(())((()))(()(())((()))))
   (()(())(()(()))(()(()(()))))
15 (()(())((()))(((())))(()(())))
   (()(())(()(()))((())(()(()))))
16 (()(())((()))(((())))((((())))))
   (()(())((()))(((())))(()((()))))
   (()(())((()))(()(()))(()((()))))
   (()(())((()))(()(()))((()(()))))
   (()(())(()(()))(()(())(()(()))))
17 (()(())((()))(((())))(()(((())))))
   (()(())((()))(((())))((())((()))))
   (()(())((()))(()(()))(()(()(()))))
   (()(())((()))(()(()))((())((()))))
18 (()(())((()))(((())))((())(((())))))
   (()(())((()))(((())))(()(())((()))))
   (()(())((()))(()(()))((())(()(()))))
   (()(())((()))(()(()))(()(())((()))))
   (()(())((()))((()((()))))(()((()))))
   (()(())((()))(()((())))((())((()))))
		

Crossrefs

Programs

  • Mathematica
    transfins[n_]:=transfins[n]=If[n===1,{{}},Select[Union@@FixedPointList[Complement[Union@@Function[fin,Cases[Complement[Subsets[fin],fin],sub_:>With[{nov=Sort[Append[fin,sub]]},nov/;Count[nov,_List,{0,Infinity}]<=n]]]/@#,#]&,Array[transfins,n-1,1,Union]],Count[#,_List,{0,Infinity}]===n&]];
    Table[Length[transfins[n]],{n,20}]

A305829 Factor n into distinct Fermi-Dirac primes (A050376), normalize by replacing every instance of the k-th Fermi-Dirac prime with k, then multiply everything together.

Original entry on oeis.org

1, 1, 2, 3, 4, 2, 5, 3, 6, 4, 7, 6, 8, 5, 8, 9, 10, 6, 11, 12, 10, 7, 12, 6, 13, 8, 12, 15, 14, 8, 15, 9, 14, 10, 20, 18, 16, 11, 16, 12, 17, 10, 18, 21, 24, 12, 19, 18, 20, 13, 20, 24, 21, 12, 28, 15, 22, 14, 22, 24, 23, 15, 30, 27, 32, 14, 24, 30, 24, 20, 25
Offset: 1

Views

Author

Gus Wiseman, Jun 10 2018

Keywords

Comments

Let f(n) = A050376(n) be the n-th Fermi-Dirac prime. Every positive integer n has a unique factorization of the form n = f(s_1)*...*f(s_k) where the s_i are strictly increasing positive integers. Then a(n) = s_1 * ... * s_k.
Multiplicative because for coprime m and n the Fermi-Dirac factorizations of m and n are disjoint and their union is the Fermi-Dirac factorization of m * n. - Andrew Howroyd, Aug 02 2018

Crossrefs

Programs

  • Mathematica
    nn=100;
    FDfactor[n_]:=If[n===1,{},Sort[Join@@Cases[FactorInteger[n],{p_,k_}:>Power[p,Cases[Position[IntegerDigits[k,2]//Reverse,1],{m_}->2^(m-1)]]]]];
    FDprimeList=Array[FDfactor,nn,1,Union];FDrules=MapIndexed[(#1->#2[[1]])&,FDprimeList];
    Table[Times@@(FDfactor[n]/.FDrules),{n,nn}]
  • PARI
    \\ here isfd is membership test for A050376.
    isfd(n)={my(e=isprimepower(n)); e && e == 1<Andrew Howroyd, Aug 02 2018

A279614 a(1)=1, a(d(x_1)*..*d(x_k)) = 1+a(x_1)+..+a(x_k) where d(n) = n-th Fermi-Dirac prime.

Original entry on oeis.org

1, 2, 3, 4, 5, 4, 6, 5, 5, 6, 7, 6, 6, 7, 7, 6, 7, 6, 8, 8, 8, 8, 7, 7, 7, 7, 7, 9, 8, 8, 8, 7, 9, 8, 10, 8, 7, 9, 8, 9, 8, 9, 7, 10, 9, 8, 9, 8, 9, 8, 9, 9, 9, 8, 11, 10, 10, 9, 9, 10, 8, 9, 10, 9, 10, 10, 8, 10, 9, 11, 8, 9, 8, 8, 9, 11, 12, 9, 8, 10, 10, 9
Offset: 1

Views

Author

Gus Wiseman, Dec 15 2016

Keywords

Comments

A Fermi-Dirac prime (A050376) is a positive integer of the form p^(2^k) where p is prime and k>=0.
In analogy with the Matula-Goebel correspondence between rooted trees and positive integers (see A061775), the iterated normalized Fermi-Dirac representation gives a correspondence between rooted identity trees and positive integers. Then a(n) is the number of nodes in the rooted identity tree corresponding to n.

Examples

			Sequence of rooted identity trees represented as finitary sets begins:
{}, {{}}, {{{}}}, {{{{}}}}, {{{{{}}}}}, {{}{{}}}, {{{{{{}}}}}},
{{}{{{}}}}, {{{}{{}}}}, {{}{{{{}}}}}, {{{{{{{}}}}}}}, {{{}}{{{}}}},
{{{}{{{}}}}}, {{}{{{{{}}}}}}, {{{}}{{{{}}}}}, {{{{}{{}}}}},
{{{}{{{{}}}}}}, {{}{{}{{}}}}, {{{{{{{{}}}}}}}}, {{{{}}}{{{{}}}}},
{{{}}{{{{{}}}}}}, {{}{{{{{{}}}}}}}, {{{{}}{{{}}}}}, {{}{{}}{{{}}}}.
		

Crossrefs

Programs

  • Mathematica
    nn=200;
    FDfactor[n_]:=If[n===1,{},Sort[Join@@Cases[FactorInteger[n],{p_,k_}:>Power[p,Cases[Position[IntegerDigits[k,2]//Reverse,1],{m_}->2^(m-1)]]]]];
    FDprimeList=Array[FDfactor,nn,1,Union];
    FDweight[n_?(#<=nn&)]:=If[n===1,1,1+Total[FDweight[Position[FDprimeList,#][[1,1]]]&/@FDfactor[n]]];
    Array[FDweight,nn]

Formula

Number of appearances of n is |a^{-1}(n)| = A004111(n).

A299759 Triangle read by rows in which row n lists in order all FDH numbers of strict integer partitions of n.

Original entry on oeis.org

1, 2, 3, 4, 6, 5, 8, 7, 10, 12, 9, 14, 15, 24, 11, 18, 20, 21, 30, 13, 22, 27, 28, 40, 42, 16, 26, 33, 35, 36, 54, 56, 60, 17, 32, 39, 44, 45, 66, 70, 72, 84, 120, 19, 34, 48, 52, 55, 63, 78, 88, 90, 105, 108, 168, 23, 38, 51, 64, 65, 77, 96, 104, 110, 126
Offset: 1

Views

Author

Gus Wiseman, Feb 18 2018

Keywords

Comments

Let f(n) = A050376(n) be the n-th Fermi-Dirac prime. Every positive integer n has a unique factorization of the form n = f(s_1)*...*f(s_k) where the s_i are strictly increasing positive integers. This determines a unique strict integer partition (s_k...s_1) whose FDH number is then defined to be n.
This sequence is a permutation of the positive integers.

Examples

			Triangle of strict partitions begins:
                  0
                 (1)
                 (2)
               (3) (21)
               (4) (31)
             (5) (41) (32)
          (6) (51) (42) (321)
        (7) (61) (43) (52) (421)
     (8) (71) (62) (53) (431) (521)
(9) (81) (72) (54) (63) (621) (531) (432).
		

Crossrefs

Programs

  • Mathematica
    nn=25;
    FDprimeList=Select[Range[nn],MatchQ[FactorInteger[#],{{?PrimeQ,?(MatchQ[FactorInteger[2#],{{2,_}}]&)}}]&];
    Table[Sort[Times@@FDprimeList[[#]]&/@Select[IntegerPartitions[n],UnsameQ@@#&]],{n,0,Length[FDprimeList]}]

A305830 Combined weight of the n-th FDH set-system. Factor n into distinct Fermi-Dirac primes (A050376), normalize by replacing every instance of the k-th Fermi-Dirac prime with k, then add up their FD-weights (A064547).

Original entry on oeis.org

0, 0, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 2, 1, 2, 2, 1, 2, 3, 2, 2, 2, 2, 1, 2, 2, 2, 3, 1, 1, 3, 2, 1, 2, 2, 2, 3, 2, 1, 2, 2, 1, 3, 3, 2, 3, 2, 2, 2, 2, 2, 3, 1, 2, 3, 2, 3, 2, 3, 3, 3, 2, 1, 3, 2, 1, 2, 2, 2, 3, 2, 2, 2, 1, 1, 3, 3, 2, 3
Offset: 1

Views

Author

Gus Wiseman, Jun 10 2018

Keywords

Comments

Let f(n) = A050376(n) be the n-th Fermi-Dirac prime. Every positive integer n has a unique factorization of the form n = f(s_1)*...*f(s_k) where the s_i are strictly increasing positive integers. Then a(n) = w(s_1) + ... + w(s_k) where w = A064547.

Examples

			Sequence of FDH set-systems (a list containing all finite sets of finite sets of positive integers) begins:
   1: {}
   2: {{}}
   3: {{1}}
   4: {{2}}
   5: {{3}}
   6: {{},{1}}
   7: {{4}}
   8: {{},{2}}
   9: {{1,2}}
  10: {{},{3}}
  11: {{5}}
  12: {{1},{2}}
  13: {{1,3}}
  14: {{},{4}}
  15: {{1},{3}}
  16: {{6}}
  17: {{1,4}}
  18: {{},{1,2}}
  19: {{7}}
  20: {{2},{3}}
  21: {{1},{4}}
  22: {{},{5}}
  23: {{2,3}}
  24: {{},{1},{2}}
  25: {{8}}
  26: {{},{1,3}}
  27: {{1},{1,2}}
		

Crossrefs

Programs

  • Mathematica
    nn=100;
    FDfactor[n_]:=If[n===1,{},Sort[Join@@Cases[FactorInteger[n],{p_,k_}:>Power[p,Cases[Position[IntegerDigits[k,2]//Reverse,1],{m_}->2^(m-1)]]]]];
    FDprimeList=Array[FDfactor,nn,1,Union];FDrules=MapIndexed[(#1->#2[[1]])&,FDprimeList];
    Table[Total[Length/@(FDfactor/@(FDfactor[n]/.FDrules))],{n,nn}]

A316202 Number of integer partitions of n into Fermi-Dirac primes.

Original entry on oeis.org

1, 0, 1, 1, 2, 2, 3, 4, 5, 7, 8, 11, 13, 17, 20, 25, 31, 37, 45, 54, 65, 77, 92, 109, 128, 152, 177, 208, 242, 283, 327, 380, 439, 506, 583, 669, 768, 878, 1004, 1144, 1303, 1482, 1681, 1906, 2156, 2438, 2750, 3101, 3490, 3924, 4407, 4942, 5538, 6197, 6929
Offset: 0

Views

Author

Gus Wiseman, Jun 26 2018

Keywords

Comments

A Fermi-Dirac prime (A050376) is a number of the form p^(2^k) where p is prime and k >= 0.

Examples

			The a(12) = 13 integer partitions of 12 into Fermi-Dirac primes:
(75), (93),
(444), (543), (552), (732),
(3333), (4332), (4422), (5322),
(33222), (42222),
(222222).
		

Crossrefs

Programs

  • Mathematica
    nn=60;
    FDpQ[n_]:=With[{f=FactorInteger[n]},n>1&&Length[f]==1&&MatchQ[FactorInteger[2f[[1,2]]],{{2,_}}]]
    FDprimeList=Select[Range[nn],FDpQ];
    ser=Product[1/(1-x^d),{d,FDprimeList}];
    Table[SeriesCoefficient[ser,{x,0,n}],{n,0,nn}]

Formula

O.g.f.: Product_d 1/(1 - x^d) where the product is over all Fermi-Dirac primes (A050376).

A322027 Maximum order of primeness among the prime factors of n; a(1) = 0.

Original entry on oeis.org

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

Views

Author

Gus Wiseman, Nov 24 2018

Keywords

Comments

The order of primeness (A078442) of a prime number p is the number of times one must apply A000720 to obtain a nonprime number.

Examples

			a(105) = 3 because the prime factor of 105 = 3*5*7 with maximum order of primeness is 5, with order 3.
		

Crossrefs

Programs

  • Maple
    with(numtheory):
    p:= proc(n) option remember;
          `if`(isprime(n), 1+p(pi(n)), 0)
        end:
    a:= n-> max(0, map(p, factorset(n))):
    seq(a(n), n=1..120);  # Alois P. Heinz, Nov 24 2018
  • Mathematica
    Table[If[n==1,0,Max@@(Length[NestWhileList[PrimePi,PrimePi[#],PrimeQ]]&/@FactorInteger[n][[All,1]])],{n,100}]

A279863 Number of maximal transitive finitary sets with n brackets.

Original entry on oeis.org

0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 2, 2, 1, 1, 4, 3, 4, 2, 5, 6, 10, 8, 11, 11, 20, 22, 29, 36, 45, 53, 77, 83, 108, 141, 172, 208, 274, 323
Offset: 1

Views

Author

Gus Wiseman, Dec 21 2016

Keywords

Comments

A finitary set is transitive if every element is also a subset. A set system is maximal if the union is also a member.

Examples

			The a(23)=3 maximal transitive finitary sets are:
(()(())(()(()))((())(()(())))(()(())(()(())))),
(()(())((()))(((())))(()((())))(()(())((())))),
(()(())((()))(()(()))(()((())))(()(())((())))).
		

Crossrefs

Programs

  • Mathematica
    maxtransfins[n_]:=If[n===1,{},Select[Union@@FixedPointList[Complement[Union@@Function[fin,Cases[Complement[Subsets[fin],fin],sub_:>With[{nov=Sort[Append[fin,sub]]},nov/;Count[Union[nov,{Union@@nov}],_List,{0,Infinity}]<=n]]]/@#,#]&,{{}}],And[Count[#,_List,{0,Infinity}]===n,MemberQ[#,Union@@#]]&]];
    Table[Length[maxtransfins[n]],{n,20}]
Showing 1-10 of 16 results. Next