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 1-9 of 9 results.

A047916 Triangular array read by rows: a(n,k) = phi(n/k)*(n/k)^k*k! if k|n else 0 (1<=k<=n).

Original entry on oeis.org

1, 2, 2, 6, 0, 6, 8, 8, 0, 24, 20, 0, 0, 0, 120, 12, 36, 48, 0, 0, 720, 42, 0, 0, 0, 0, 0, 5040, 32, 64, 0, 384, 0, 0, 0, 40320, 54, 0, 324, 0, 0, 0, 0, 0, 362880, 40, 200, 0, 0, 3840, 0, 0, 0, 0, 3628800, 110, 0, 0, 0, 0, 0, 0, 0, 0, 0, 39916800, 48, 144
Offset: 1

Views

Author

Keywords

Comments

T(n,k) = A054523(n,k) * A010766(n,k)^A002260(n,k) * A166350(n,k). - Reinhard Zumkeller, Jan 20 2014

Examples

			1; 2,2; 6,0,6; 8,8,0,24; 20,0,0,0,120; 12,36,48,0,0,720; ...
		

References

  • J. E. A. Steggall, On the numbers of patterns which can be derived from certain elements, Mess. Math., 37 (1907), 56-61.

Crossrefs

A064649 gives the row sums.
Cf. A002618 (left edge), A000142 (right edge), A049820 (zeros per row), A000005 (nonzeros per row).
See also A247917, A047918, A047919.

Programs

  • Haskell
    import Data.List (zipWith4)
    a047916 n k = a047916_tabl !! (n-1) !! (k-1)
    a047916_row n = a047916_tabl !! (n-1)
    a047916_tabl = zipWith4 (zipWith4 (\x u v w -> x * v ^ u * w))
                   a054523_tabl a002260_tabl a010766_tabl a166350_tabl
    -- Reinhard Zumkeller, Jan 20 2014
    
  • Mathematica
    a[n_, k_] := If[Divisible[n, k], EulerPhi[n/k]*(n/k)^k*k!, 0]; Flatten[ Table[ a[n, k], {n, 1, 12}, {k, 1, n}]] (* Jean-François Alcover, May 04 2012 *)
  • PARI
    a(n,k)=if(n%k, 0, eulerphi(n/k)*(n/k)^k*k!) \\ Charles R Greathouse IV, Feb 09 2017

A269221 Factorial of the sum of decimal digits of n.

Original entry on oeis.org

1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 24, 120, 720, 5040
Offset: 0

Views

Author

M. F. Hasler, Mar 15 2016

Keywords

Comments

Sequence A093659 is the binary (base 2) version.

Crossrefs

Programs

  • Mathematica
    Table[Total[IntegerDigits[n]]!,{n,0,50}] (* Harvey P. Dale, Dec 19 2021 *)
  • PARI
    A269221(n)=sumdigits(n)!

Formula

a(n) = A000142(A007953(n)).

A288777 Triangle read by rows in which column k lists the positive multiples of the factorial of k, with 1 <= k <= n.

Original entry on oeis.org

1, 2, 2, 3, 4, 6, 4, 6, 12, 24, 5, 8, 18, 48, 120, 6, 10, 24, 72, 240, 720, 7, 12, 30, 96, 360, 1440, 5040, 8, 14, 36, 120, 480, 2160, 10080, 40320, 9, 16, 42, 144, 600, 2880, 15120, 80640, 362880, 10, 18, 48, 168, 720, 3600, 20160, 120960, 725760, 3628800, 11, 20, 54, 192, 840, 4320, 25200, 161280, 1088640
Offset: 1

Views

Author

Omar E. Pol, Jun 15 2017

Keywords

Comments

T(n,k) is the number of k-digit numbers in base n+1 with distinct positive digits that form an integer interval when sorted.
T(9,k) is also the number of numbers with k digits in A288528.
The number of terms in A288528 is also A014145(9) = 462331, the same as the sum of the 9th row of this triangle.
Removing the left column of A137267 and of A137948 then this triangle appears in both cases.

Examples

			Triangle begins:
   1;
   2,  2;
   3,  4,  6;
   4,  6, 12,  24;
   5,  8, 18,  48, 120;
   6, 10, 24,  72, 240,  720;
   7, 12, 30,  96, 360, 1440,  5040;
   8, 14, 36, 120, 480, 2160, 10080,  40320;
   9, 16, 42, 144, 600, 2880, 15120,  80640,  362880;
  10, 18, 48, 168, 720, 3600, 20160, 120960,  725760, 3628800;
  11, 20, 54, 192, 840, 4320, 25200, 161280, 1088640, 7257600, 39916800;
  ...
For n = 9 and k = 2: T(9,2) is the number of numbers with two digits in A288528.
For n = 9 the row sum is 9 + 16 + 42 + 144 + 600 + 2880 + 15120 + 80640 + 362880 = 462331, the same as A014145(9) and also the same as the number of terms in A288528.
		

Crossrefs

Right border gives A000142, n>=1.
Middle diagonal gives A001563, n>=1.
Row sums give A014145, n>=1.
Column 1..4: A000027, A005843, A008588, A008606.

Programs

  • Mathematica
    Table[(n - k + 1) k!, {n, 11}, {k, n}] // Flatten (* Michael De Vlieger, Jun 15 2017 *)

Formula

T(n,k) = (n-k+1)*k! = (n-k+1)*A000142(k) = A004736(n,k)*A166350(n,k).
T(n,k) = Sum_{j=1..n} A166350(j,k).
T(n,k) = A288778(n,k) + A000142(k-1).

A014454 Sum_{1<=k

Original entry on oeis.org

0, 1, 2, 5, 6, 21, 22, 73, 210, 1693, 1694, 2097, 2098, 12997, 21468, 174169, 174170, 1986237, 1986238, 10178833, 16875654, 246551437, 246551438, 2032266537, 3767596738, 45445808989, 260705796192, 2932954933753, 2932954933754, 5496591783573, 5496591783574
Offset: 1

Views

Author

Reinhard Zumkeller, Feb 12 2002

Keywords

Examples

			a(5) = gcd(1!,5!)+gcd(2!,3*4*5)+gcd(3!,4*5)+gcd(4!,5)=1+2+2+1 = 6.
		

Crossrefs

Cf. A000142.
Cf. A166350.

Programs

  • Haskell
    a014454 n = sum $ zipWith gcd kfs $ map (div nf) kfs
       where (nf:kfs) = reverse $ a166350_row n
    -- Reinhard Zumkeller, Nov 11 2013
  • PARI
    a(n) = sum(k=1, n-1, gcd(k!, n!/k!)); \\ Michel Marcus, Aug 04 2013
    

A269223 Factorial of the sum of digits of n in base 3.

Original entry on oeis.org

1, 1, 2, 1, 2, 6, 2, 6, 24, 1, 2, 6, 2, 6, 24, 6, 24, 120, 2, 6, 24, 6, 24, 120, 24, 120, 720, 1, 2, 6, 2, 6, 24, 6, 24, 120, 2, 6, 24, 6, 24, 120, 24, 120, 720, 6, 24, 120, 24, 120, 720, 120, 720, 5040, 2, 6, 24, 6, 24, 120, 24, 120, 720, 6, 24, 120, 24, 120, 720, 120, 720
Offset: 0

Views

Author

M. F. Hasler, Mar 15 2016

Keywords

Comments

Sequence A093659 is the binary (base 2) and sequence A269221 is the decimal (base 10) version.

Crossrefs

Programs

  • Mathematica
    Table[Total[IntegerDigits[n, 3]]!, {n, 0, 70}] (* Michael De Vlieger, Mar 15 2016 *)
  • PARI
    A269223(n)=sumdigits(n,3)! \\ sumdigits(.,3) requires version > 2.7.1; see A053735 for a substitute.
    
  • PARI
    a(n) = vecsum(digits(n,3))!; \\ Michel Marcus, Mar 15 2016

Formula

a(n) = A000142(A053735(n)).

A288778 Triangle read by rows (1<=k<=n): T(n,k) = (n-k+1)*k! - (k-1)!

Original entry on oeis.org

0, 1, 1, 2, 3, 4, 3, 5, 10, 18, 4, 7, 16, 42, 96, 5, 9, 22, 66, 216, 600, 6, 11, 28, 90, 336, 1320, 4320, 7, 13, 34, 114, 456, 2040, 9360, 35280, 8, 15, 40, 138, 576, 2760, 14400, 75600, 322560, 9, 17, 46, 162, 696, 3480, 19440, 115920, 685440, 3265920, 10, 19, 52, 186, 816, 4200, 24480, 156240, 1048320, 6894720, 36288000
Offset: 1

Views

Author

Omar E. Pol, Jun 15 2017

Keywords

Comments

T(10,k) is also the number of positive integers with k digits in the sequence A215014. See Franklin T. Adams-Watters's comment in that entry. See also A288780.

Examples

			Triangle begins:
0;
1,   1;
2,   3,  4;
3,   5, 10,  18;
4,   7, 16,  42,  96;
5,   9, 22,  66, 216,  600;
6,  11, 28,  90, 336, 1320,  4320;
7,  13, 34, 114, 456, 2040,  9360,  35280;
8,  15, 40, 138, 576, 2760, 14400,  75600,  322560;
9,  17, 46, 162, 696, 3480, 19440, 115920,  685440, 3265920;
10, 19, 52, 186, 816, 4200, 24480, 156240, 1048320, 6894720, 36288000;
...
For n = 10 and k = 2; T(10,2) = 17 coincides with the number of positive terms with two digits in A215014 (see the first comment above).
		

Crossrefs

Column 1 gives A001477.
Row sums give A288780.

Programs

  • Mathematica
    Table[(n - k + 1) k! - (k - 1)!, {n, 11}, {k, n}] // Flatten (* Michael De Vlieger, Jun 16 2017 *)

Formula

T(n,k) = A288777(n,k) - A000142(k-1), n>=1.

A256589 Triangle read by rows: T(n,k) divided by (n-k+1)! is the expected value of number of possible subsets in a partition of a set of n elements with no subsets of cardinality smaller than k.

Original entry on oeis.org

1, 3, 1, 11, 2, 1, 50, 8, 2, 1, 274, 36, 6, 2, 1, 1764, 200, 30, 6, 2, 1, 13068, 1300, 168, 24, 6, 2, 1, 109584, 9720, 1080, 144, 24, 6, 2, 1, 1026576, 82180, 8100, 960, 120, 24, 6, 2, 1
Offset: 1

Views

Author

Martin Y. Champel, Apr 03 2015

Keywords

Comments

This sequence can be seen as a generalization of A233744 which is the particular case where minimum subset cardinality is 2 (k=2).
T(n,k) / A004736(n,k)! = 1 + 1 / ( A002024(n,k) - A002260(n,k) + 1) * (Sum of (T(n,p) / A004736(n,p)!) for p starting at A002260(n,k) up to A002024(n) - A002260(n) if 2 * A002260(n) <= A002024(n)).
The triangle below but including the diagonal is A166350 because there is only one possible partition of subsets of cardinality >= k in any set whose cardinality is between k and 2*k-1.

Examples

			The triangle T(n, k) starts:
n\k  1   2   3  4  5  6  ...
1:   1
2:   3   1
3:  11   2   1
4:  50   8   2  1
5: 274  36   6  2  1
6:1764 200  36  6  2  1
		

Crossrefs

A269224 Factorial of the sum of digits of n in base 4.

Original entry on oeis.org

1, 1, 2, 6, 1, 2, 6, 24, 2, 6, 24, 120, 6, 24, 120, 720, 1, 2, 6, 24, 2, 6, 24, 120, 6, 24, 120, 720, 24, 120, 720, 5040, 2, 6, 24, 120, 6, 24, 120, 720, 24, 120, 720, 5040, 120, 720, 5040, 40320, 6, 24, 120, 720, 24, 120, 720, 5040, 120, 720, 5040, 40320, 720, 5040, 40320
Offset: 0

Views

Author

M. F. Hasler, Mar 15 2016

Keywords

Comments

See sequences A093659, A269223 and A269221 for the base 2, base 3 and base 10 analog.

Crossrefs

Programs

  • Mathematica
    Table[Total[IntegerDigits[n, 4]]!, {n, 0, 62}] (* Michael De Vlieger, Mar 15 2016 *)
  • PARI
    A269224(n)=sumdigits(n,4)! \\ sumdigits(.,4) requires version >= 2.7; see A053737 for a substitute.
    
  • PARI
    a(n) = vecsum(digits(n,4))!; \\ Michel Marcus, Mar 15 2016

Formula

a(n) = A000142(A053737(n)).

A233543 Triangle read by rows: T(n,k) = k!.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 2, 6, 1, 1, 2, 6, 24, 1, 1, 2, 6, 24, 120, 1, 1, 2, 6, 24, 120, 720, 1, 1, 2, 6, 24, 120, 720, 5040, 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800
Offset: 0

Views

Author

Paul Curtz, Dec 12 2013

Keywords

Examples

			Triangle begins:
  1;
  1, 1;
  1, 1, 2;
  1, 1, 2, 6;
  1, 1, 2, 6, 24;
  1, 1, 2, 6, 24, 120;
  ...
		

Crossrefs

Row sums give A003422(n+1).

Programs

Formula

T(n,k) = A000142(k).
Showing 1-9 of 9 results.