A181842 -id:A181842 - cp's OEIS frontend

A181843 Triangle read by rows: Partial row sums of A181842.

1, 1, 3, 1, 3, 6, 1, 3, 8, 12, 1, 3, 8, 18, 23, 1, 3, 8, 20, 32, 38, 1, 3, 8, 20, 38, 66, 73, 1, 3, 8, 20, 40, 78, 110, 118, 1, 3, 8, 20, 40, 84, 141, 189, 198, 1, 3, 8, 20, 40, 86, 153, 253, 308, 318, 1, 3, 8, 20, 40, 86, 159, 287, 409, 519, 530, 1, 3, 8, 20, 40, 86, 161, 299, 476, 728, 807, 819

Offset: 1

Peter Luschny, Dec 07 2010

			[1]   1
[2]   1   3
[3]   1   3   6
[4]   1   3   8   12
[5]   1   3   8   18   23
[6]   1   3   8   20   32   38
[7]   1   3   8   20   38   66   73

Cf. A181842, A181844.

with(combstruct):
a181843_row := proc(n) local k,L,l,R,part;
R := NULL; L := 0;
for k from 1 to n do
   part := iterstructs(Partition(n),size=n-k+1):
   while not finished(part) do
      l := nextstruct(part);
      L := L + ilcm(op(l));
   od;
   R := R,L;
od;
R end:

t[n_, k_] := LCM @@@ IntegerPartitions[n, {n - k + 1}] // Total; row[n_] := Table[t[n, k], {k, 1, n}] // Accumulate; Table[row[n], {n, 1, 12}] // Flatten (* Jean-François Alcover, Jul 26 2013 *)

Terms from an erroneous copy and paste transfer corrected.

More terms from Jean-François Alcover, Jul 26 2013

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

Peter Luschny, Dec 07 2010

nonn

Old name was: Row sums of A181842.

Alois P. Heinz, Table of n, a(n) for n = 0..188 (terms n=1..80 from Vincenzo Librandi)

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

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

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 *)

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

a(0)=1 prepended by Alois P. Heinz, Mar 29 2015

New name from Alois P. Heinz, Mar 18 2019

A181853 Triangle read by rows: T(n,k) = Sum_{c in C(n,k)} lcm(c) where C(n,k) is the set of all k-subsets of {1,2,...,n}.

Original entry on oeis.org

1, 1, 1, 1, 3, 2, 1, 6, 11, 6, 1, 10, 31, 34, 12, 1, 15, 81, 189, 182, 60, 1, 21, 141, 393, 494, 282, 60, 1, 28, 288, 1380, 3245, 3740, 2034, 420, 1, 36, 456, 2716, 8293, 13268, 11338, 4908, 840, 1, 45, 726, 5578, 22207, 47351, 57598, 40602, 15564, 2520

Offset: 0

Peter Luschny, Dec 06 2010

The C(n,k) are also called combinations of n with size k (see A181842).

Main diagonal gives: A003418. Lower diagonal gives: A094308. Column k=1 gives: A000217. - Alois P. Heinz, Jul 29 2013

			[0]   1
[1]   1    1
[2]   1    3     2
[3]   1    6    11     6
[4]   1   10    31    34    12
[5]   1   15    81   189   182    60
[6]   1   21   141   393   494   282   60

Alois P. Heinz, Rows n = 0..46, flattened

Row sums give A226037.

Cf. A065567, A096179, A181854.

with(combstruct):
a181853_row := proc(n) local k,L,l,R,comb;
R := NULL;
for k from 0 to n do
   L := 0;
   comb := iterstructs(Combination(n),size=k):
   while not finished(comb) do
      l := nextstruct(comb);
      L := L + ilcm(op(l));
   od;
   R := R,L;
od;
R end:
# second Maple program:
b:= proc(n, k) option remember; `if`(k=0, [1],
     [`if`(k add(c, c=b(n, k)):
seq(seq(T(n, k), k=0..n), n=0..10);  # Alois P. Heinz, Jul 29 2013
# third Maple program:
b:= proc(n, m) option remember; expand(`if`(n=0, m,
      b(n-1, ilcm(m, n))*x+b(n-1, m)))
    end:
T:= n-> (p-> seq(coeff(p, x, i), i=0..n))(b(n, 1)):
seq(T(n), n=0..10);  # Alois P. Heinz, Sep 05 2023

t[, 0] = 1; t[n, k_] := Sum[LCM @@ c, {c, Subsets[Range[n], {k}]}]; Table[t[n, k], {n, 0, 8}, {k, 0, n}] // Flatten (* Jean-François Alcover, Jul 29 2013 *)

# (After Alois P. Heinz)
@CachedFunction
def b(n, k):
    if k == 0: return [1]
    w = b(n-1, k) if kPeter Luschny, Jul 29 2013

A181851 Triangle read by rows: T(n,k) = Sum_{c in composition(n,k)} lcm(c).

Original entry on oeis.org

1, 2, 1, 3, 4, 1, 4, 8, 6, 1, 5, 20, 15, 8, 1, 6, 21, 50, 24, 10, 1, 7, 56, 66, 96, 35, 12, 1, 8, 60, 180, 160, 160, 48, 14, 1, 9, 96, 264, 432, 325, 244, 63, 16, 1, 10, 105, 510, 776, 892, 585, 350, 80, 18, 1, 11, 220, 567, 1704, 1835, 1668, 966, 480, 99, 20, 1

Offset: 1

Peter Luschny, Dec 07 2010

Composition(n,k) is the set of the k-tuples of positive integers which sum to n (see A181842). Taking the example in A181842, T(6,2) = lcm(5,1) + lcm(4,2) + lcm(3,3) + lcm(2,4) + lcm(1,5) = 5+4+3+4+5 = 21.

			[1]   1
[2]   2    1
[3]   3    4    1
[4]   4    8    6    1
[5]   5   20   15    8    1
[6]   6   21   50   24   10    1
[7]   7   56   66   96   35   12   1

Alois P. Heinz, Rows n = 1..150, flattened

Cf. A181849, A181850, A181853.

T(2n,n) gives A373865.

with(combstruct):
a181851_row := proc(n) local k,L,l,R,comp;
R := NULL;
for k from 1 to n do
   L := 0;
   comp := iterstructs(Composition(n),size=k):
   while not finished(comp) do
      l := nextstruct(comp);
      L := L + ilcm(op(l));
   od;
   R := R,L;
od;
R end:

c[n_, k_] := Permutations /@ IntegerPartitions[n, {k}] // Flatten[#, 1]&; t[n_, k_] := Total[LCM @@@ c[n, k]]; Table[t[n, k], {n, 1, 11}, {k, 1, n}] // Flatten (* Jean-François Alcover, Feb 05 2014 *)

A181847 Triangle read by rows: T(n,k)= Sum_{c in C(n,k)}gcd(c) where C(n,k) is the set of all k-tuples of positive integers whose elements sum to n.

Original entry on oeis.org

1, 2, 1, 3, 2, 1, 4, 4, 3, 1, 5, 4, 6, 4, 1, 6, 9, 11, 10, 5, 1, 7, 6, 15, 20, 15, 6, 1, 8, 12, 24, 36, 35, 21, 7, 1, 9, 12, 30, 56, 70, 56, 28, 8, 1, 10, 17, 42, 88, 127, 126, 84, 36, 9, 1

Offset: 1

Peter Luschny, Dec 07 2010

C(n,k) counted by A007318(n-1,k-1) are also called compositions of n of size k (see A181842).

			[1]   1
[2]   2   1
[3]   3   2    1
[4]   4   4    3    1
[5]   5   4    6    4    1
[6]   6   9   11   10    5   1
[7]   7   6   15   20   15   6   1

Cf. A034738, A065567, A065568, A327029.

with(combstruct): # By generating the objects, very inefficient.
a181847_row := proc(n) local k,L,l,R,comp; R := NULL;
for k from 1 to n do
   L := 0;
   comp := iterstructs(Composition(n),size=k):
   while not finished(comp) do
      l := nextstruct(comp);
      L := L + igcd(op(l));
   od;
   R := R,L;
od;
R end:
# second Maple program:
with(numtheory):
T := (n, k) -> add(phi(d)*binomial(n/d-1, k-1), d = divisors(n)):
seq(seq(T(n, k), k=1..n), n=1..10); # Peter Luschny, Aug 27 2019

# uses[DivisorTriangle from A327029]
# DivisorTriangle Computes the (0,0)-based version.
DivisorTriangle(euler_phi, lambda n,k: binomial(n-1, k-1), 10) # Peter Luschny, Aug 27 2019

A181845 Triangle read by rows: T(n,k) = max_{c in P(n,n-k+1)} lcm(c) where P(n,m) = A008284(n,m) is the number of partitions of n into m parts.

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 2, 3, 4, 1, 2, 3, 6, 5, 1, 2, 3, 6, 5, 6, 1, 2, 3, 6, 6, 12, 7, 1, 2, 3, 6, 6, 12, 15, 8, 1, 2, 3, 6, 6, 12, 15, 20, 9, 1, 2, 3, 6, 6, 12, 15, 30, 21, 10, 1, 2, 3, 6, 6, 12, 15, 30, 21, 30, 11, 1, 2, 3, 6, 6, 12, 15, 30, 30, 60, 35, 12

Offset: 1

Peter Luschny, Dec 07 2010

See A181842 for the definition of 'partition'. T(n,k) is also the triangle read by rows: T(n,k) = max_{c in C(n,n-k+1)} lcm(c) where C(n,m) is the set of all m-tuples of positive integers whose elements sum to n where the C(n,k) = A007318(n-1,k-1) are called compositions of n of size k.

			[1]   1
[2]   1   2
[3]   1   2   3
[4]   1   2   3   4
[5]   1   2   3   6   5
[6]   1   2   3   6   5   6
[7]   1   2   3   6   6   12   7
[8]   1   2   3   6   6   12   15   8
[9]   1   2   3   6   6   12   15   20   9

Andrew Howroyd, Table of n, a(n) for n = 1..1275 (rows 1..50)

Cf. A181842, A181843, A181844.

with(combstruct):
a181845_row := proc(n) local k,L,l,R,part;
R := NULL;
for k from 1 to n do
   L := 0;
   part := iterstructs(Partition(n),size=n-k+1):
# alternatively (but slower)
# part := iterstructs(Composition(n), size=n-k+1):
   while not finished(part) do
      l := nextstruct(part);
      L := max(L,ilcm(op(l)));
   od;
   R := R,L;
od;
R end:

Row(n)={my(v=vector(n)); forpart(p=n, my(i=#p); v[i]=max(v[i], lcm(Vec(p)))); Vecrev(v)}
{ for(n=1, 10, print(Row(n))) } \\ Andrew Howroyd, Apr 20 2021

Terms a(56) and beyond from Andrew Howroyd, Apr 20 2021

A181846 Triangle read by rows: T(n,k) = Sum_{c in P(n,n-k+1)} gcd(c) where P(n,m) = A008284(n,m) is the number of partitions of n into m parts.

Original entry on oeis.org

1, 1, 2, 1, 1, 3, 1, 1, 3, 4, 1, 1, 2, 2, 5, 1, 1, 2, 4, 6, 6, 1, 1, 2, 3, 4, 3, 7, 1, 1, 2, 3, 6, 6, 8, 8, 1, 1, 2, 3, 5, 6, 9, 6, 9, 1, 1, 2, 3, 5, 8, 10, 10, 11, 10, 1, 1, 2, 3, 5, 7, 10, 11, 10, 5, 11, 1, 1, 2, 3, 5, 7, 12, 14, 19, 19, 17, 12, 1, 1, 2, 3, 5, 7, 11, 14, 18, 18, 14, 6, 13

Offset: 1

Peter Luschny, Dec 07 2010

See A181842 for the definition of 'partition'.

			[1]   1
[2]   1   2
[3]   1   1   3
[4]   1   1   3   4
[5]   1   1   2   2   5
[6]   1   1   2   4   6   6
[7]   1   1   2   3   4   3   7

Cf. A078392.

with(combstruct):
a181846_row := proc(n) local k,L,l,R,part;
R := NULL;
for k from 1 to n do
   L := 0;
   part := iterstructs(Partition(n),size=n-k+1):
   while not finished(part) do
      l := nextstruct(part);
      L := L + igcd(op(l));
   od;
   R := R,L;
od;
R end:

T[n_, k_] := GCD @@@ IntegerPartitions[n, {n-k+1}] // Total;
Table[T[n, k], {n, 1, 13}, {k, 1, n}] (* Jean-François Alcover, Jun 22 2019 *)

Extended to 13 rows by Jean-François Alcover, Jun 22 2019

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A181843 Triangle read by rows: Partial row sums of A181842.

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

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A181853 Triangle read by rows: T(n,k) = Sum_{c in C(n,k)} lcm(c) where C(n,k) is the set of all k-subsets of {1,2,...,n}.

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A181851 Triangle read by rows: T(n,k) = Sum_{c in composition(n,k)} lcm(c).

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A181847 Triangle read by rows: T(n,k)= Sum_{c in C(n,k)}gcd(c) where C(n,k) is the set of all k-tuples of positive integers whose elements sum to n.

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A181845 Triangle read by rows: T(n,k) = max_{c in P(n,n-k+1)} lcm(c) where P(n,m) = A008284(n,m) is the number of partitions of n into m parts.

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A181846 Triangle read by rows: T(n,k) = Sum_{c in P(n,n-k+1)} gcd(c) where P(n,m) = A008284(n,m) is the number of partitions of n into m parts.

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