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 1-3 of 3 results.

A181844 Sum over all partitions of n of the LCM of the parts.

Original entry on oeis.org

1, 1, 3, 6, 12, 23, 38, 73, 118, 198, 318, 530, 819, 1298, 1974, 2975, 4516, 6698, 9980, 14550, 21186, 30304, 43503, 62030, 87908, 123292, 172543, 239720, 331688, 458198, 629376, 860332, 1168172, 1583176, 2138438, 2876283, 3859770, 5159886, 6863702, 9112356
Offset: 0

Views

Author

Peter Luschny, Dec 07 2010

Keywords

Comments

Old name was: Row sums of A181842.

Crossrefs

Cf. A078392 (the same for GCD), A181843, A181842, A256067, A256553, A256554, A306956.

Programs

  • Maple
    with(combstruct):
    a181844 := proc(n) local k,L,l,R,part;
    R := NULL; L := 0;
    for k from 1 to n do
       part := iterstructs(Partition(n),size=k):
       while not finished(part) do
          l := nextstruct(part);
          L := L + ilcm(op(l));
       od;
    od;
    L end:
    # second Maple program:
    b:= proc(n, i, r) option remember; `if`(n=0, r, `if`(i<1, 0,
           b(n, i-1, r)+b(n-i, min(i, n-i), ilcm(i, r))))
        end:
    a:= n-> b(n$2, 1):
    seq(a(n), n=0..42);  # Alois P. Heinz, Mar 18 2019
  • Mathematica
    t[n_, k_] := LCM @@@ IntegerPartitions[n, {n - k + 1}] // Total; a[n_] := Sum[t[n, k], {k, 1, n}]; Table[a[n], {n, 1, 32}] (* Jean-François Alcover, Jul 26 2013 *)

Formula

a(n) = Sum_{k>=0} k * A256067(n,k) = Sum_{k>=0} A256553(n,k)*A256554(n,k). - Alois P. Heinz, Apr 02 2015

Extensions

a(0)=1 prepended by Alois P. Heinz, Mar 29 2015
New name from Alois P. Heinz, Mar 18 2019

A256554 Number T(n,k) of cycle types of degree-n permutations having the k-th smallest possible order; triangle T(n,k), n>=0, 1<=k<=A009490(n), read by rows.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 3, 2, 2, 1, 2, 1, 3, 2, 2, 1, 3, 1, 1, 1, 1, 4, 2, 4, 1, 5, 1, 1, 1, 1, 1, 1, 4, 3, 4, 1, 7, 1, 1, 1, 2, 2, 1, 1, 1, 1, 5, 3, 6, 2, 9, 1, 2, 1, 3, 4, 1, 1, 1, 1, 1, 1, 5, 3, 6, 2, 12, 1, 2, 1, 4, 1, 6, 2, 2, 1, 2, 1, 1, 1, 2
Offset: 0

Views

Author

Alois P. Heinz, Apr 01 2015

Keywords

Comments

Sum_{k>=0} A256553(n,k)*T(n,k) = A181844(n).

Examples

			Triangle T(n,k) begins:
  1;
  1;
  1, 1;
  1, 1, 1;
  1, 2, 1, 1;
  1, 2, 1, 1, 1, 1;
  1, 3, 2, 2, 1, 2;
  1, 3, 2, 2, 1, 3, 1, 1, 1;
  1, 4, 2, 4, 1, 5, 1, 1, 1, 1, 1;
  1, 4, 3, 4, 1, 7, 1, 1, 1, 2, 2, 1, 1, 1;
  1, 5, 3, 6, 2, 9, 1, 2, 1, 3, 4, 1, 1, 1, 1, 1;
		

Crossrefs

Row sums give A000041.
Row lengths give A009490.
Columns k=1-9 give: A000012, A004526, A002264, A008642(n-4), A002266, A074752, A132270, A008643(n-8) for n>7, A008649(n-9) for n>8.
Last elements of rows give A074064.
Main diagonal gives A074761.

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0 or i=1, x,
          b(n, i-1)+(p-> add(coeff(p, x, t)*x^ilcm(t, i),
          t=1..degree(p)))(add(b(n-i*j, i-1), j=1..n/i)))
        end:
    T:= n->(p->seq((h->`if`(h=0, [][], h))(coeff(p, x, i))
         , i=1..degree(p)))(b(n$2)):
    seq(T(n), n=0..12);
  • Mathematica
    b[n_, i_] := b[n, i] = If[n == 0 || i == 1, x, b[n, i - 1] + Function[p, Sum[Coefficient[p, x, t]*x^LCM[t, i], {t, 1, Exponent[p, x]}]][Sum[b[n - i*j, i - 1], {j, 1, n/i}]]]; T[n_] := Function[p, Table[Function[h, If[h == 0, {{}, {}}, h]][Coefficient[p, x, i]], {i, 1, Exponent[p, x]}]][b[n, n]]; Table[T[n], {n, 0, 12}] // Flatten (* Jean-François Alcover, Jan 23 2017, translated from Maple *)

A060179 Sum of distinct orders of degree-n permutations.

Original entry on oeis.org

1, 1, 3, 6, 10, 21, 21, 50, 73, 116, 167, 248, 385, 496, 728, 959, 1548, 1899, 2835, 3609, 5042, 6403, 8336, 12187, 15522, 21358, 26090, 35298, 44147, 62512, 76289, 101403, 123883, 156880, 200086, 254175, 335380, 413184, 505860, 615258, 810767, 980747, 1293953
Offset: 0

Views

Author

Vladeta Jovovic, Mar 19 2001

Keywords

Examples

			Set of orders of all degree 7 permutations is {1,2,3,4,5,6,7,10,12} so a(7)=1+2+3+4+5+6+7+10+12=50.
		

Crossrefs

Cf. A009490.
Row sums of A256553.

Programs

  • Maple
    b:= proc(n, i) option remember; (p->`if`(i*n=0, 1,
           add(b(n-p^j, i-1)*p^j, j=1..ilog[p](n))+
             b(n, i-1)))(`if`(i=0, 0, ithprime(i)))
        end:
    a:= n-> b(n, numtheory[pi](n)):
    seq(a(n), n=0..50);  # Alois P. Heinz, Jul 12 2017
  • Mathematica
    b[n_, i_] := b[n, i] = Function [p, If[i*n == 0, 1, Sum[b[n-p^j, i-1]*p^j, {j, 1, Floor@Log[p, n]}] + b[n, i-1]]][If[i == 0, 0, Prime[i]]];
    a[n_] := b[n, PrimePi[n]];
    a /@ Range[0, 50] (* Jean-François Alcover, Mar 14 2021, after Alois P. Heinz *)

Formula

G.f.: Prod(p prime, 1 + Sum(k >= 1, p^k*x^(p^k))) / (1-x). - Vladeta Jovovic, Sep 18 2002

Extensions

More terms from David Wasserman, May 29 2002
a(0)=1 prepended by Alois P. Heinz, Apr 01 2015
Showing 1-3 of 3 results.