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 1-5 of 5 results.

A203317 a(n) = A203315(n)/A000178(n) where A000178=(superfactorials).

Original entry on oeis.org

1, 2, 8, 256, 10240, 3440640, 1233125376, 4058744094720, 286551971651911680, 13351029463205868994560, 18128348229848045861669437440, 80945830355202461675325011924090880, 223346912509970707926726595810215906508800
Offset: 1

Views

Author

Clark Kimberling, Jan 01 2012

Keywords

Links

Crossrefs

Cf. A203315, A203316, A000040.

Programs

  • Mathematica
    f[j_] := Prime[j + 1]; z = 17;
v[n_] := Product[Product[f[k] - f[j], {j, 1, k - 1}], {k, 2, n}]
d[n_] := Product[(i - 1)!, {i, 1, n}]
Table[v[n], {n, 1, z}]                  (* A203315 *)
Table[v[n + 1]/(2 v[n]), {n, 1, z - 1}] (* A203316 *)
Table[v[n]/d[n], {n, 1, 20}]            (* A203317 *)

A203316 a(n) = v(n+1)/(2*v(n)), where v=A203315.

Original entry on oeis.org

1, 4, 96, 480, 20160, 129024, 8294400, 1423319040, 8453652480, 2463635865600, 89117289676800, 660834091008000, 63038756487168000, 20712734274355200000, 4023397460155878604800, 27460572284725493760000
Offset: 1

Views

Author

Clark Kimberling, Jan 01 2012

Keywords

Crossrefs

Cf. A203315, A203317, A000040.

Programs

  • Mathematica
    f[j_] := Prime[j + 1]; z = 17;
v[n_] := Product[Product[f[k] - f[j], {j, 1, k - 1}], {k, 2, n}]
d[n_] := Product[(i - 1)!, {i, 1, n}]
Table[v[n], {n, 1, z}]                  (* A203315 *)
Table[v[n + 1]/(2 v[n]), {n, 1, z - 1}] (* A203316 *)
Table[v[n]/d[n], {n, 1, 20}]            (* A203317 *)

Extensions

Definition corrected by Georg Fischer, Nov 26 2021

A093883 Product of all possible sums of two distinct numbers taken from among first n natural numbers.

Original entry on oeis.org

1, 3, 60, 12600, 38102400, 2112397056000, 2609908810629120000, 84645606509847871488000000, 82967862872337478796810649600000000, 2781259372192376861719959017613164544000000000
Offset: 1

Views

Author

Amarnath Murthy, Apr 22 2004

Keywords

Comments

From Clark Kimberling, Jan 02 2013: (Start)
Each term divides its successor, as in A006963, and by the corresponding superfactorial, A000178(n), as in A203469.
Abbreviate "Vandermonde" as V. The V permanent of a set S={s(1),s(2),...,s(n)} is a product of sums s(j)+s(k) in analogy to the V determinant as a product of differences s(k)-s(j). Let D(n) and P(n) denote the V determinant and V permanent of S, and E(n) the V determinant of the numbers s(1)^2, s(2)^2, ..., s(n)^2; then P(n) = E(n)/D(n). This is one of many divisibility properties associated with V determinants and permanents. Another is that if S consists of distinct positive integers, then D(n) divides D(n+1) and P(n) divides P(n+1).
Guide to related sequences:
...
s(n).............. D(n)....... P(n)
n................. A000178.... (this)
n+1............... A000178.... A203470
n+2............... A000178.... A203472
n^2............... A202768.... A203475
2^(n-1)........... A203303.... A203477
2^n-1............. A203305.... A203479
n!................ A203306.... A203482
n(n+1)/2.......... A203309.... A203511
Fibonacci(n+1).... A203311.... A203518
prime(n).......... A080358.... A203521
odd prime(n)...... A203315.... A203524
nonprime(n)....... A203415.... A203527
composite(n)...... A203418.... A203530
2n-1.............. A108400.... A203516
n+floor(n/2)...... A203430
n+floor[(n+1)/2].. A203433
1/n............... A203421
1/(n+1)........... A203422
1/(2n)............ A203424
1/(2n+2).......... A203426
1/(3n)............ A203428
Generalizing, suppose that f(x,y) is a function of two variables and S=(s(1),s(2),...s(n)). The phrase, "Vandermonde sequence using f(x,y) applied to S" means the sequence a(n) whose n-th term is the product f(s(j,k)) : 1<=j
...
If f(x,y) is a (bivariate) cyclotomic polynomial and S is a strictly increasing sequence of positive integers, then a(n) consists of integers, each of which divides its successor. Guide to sequences for which f(x,y) is x^2+xy+y^2 or x^2-xy+y^2 or x^2+y^2:
...
s(n) ............ x^2+xy+y^2.. x^2-xy+y^2.. x^2+y^2
n ............... A203012..... A203312..... A203475
n+1 ............. A203581..... A203583..... A203585
2n-1 ............ A203514..... A203587..... A203589
n^2 ............. A203673..... A203675..... A203677
2^(n-1) ......... A203679..... A203681..... A203683
n! .............. A203685..... A203687..... A203689
n(n+1)/2 ........ A203691..... A203693..... A203695
Fibonacci(n) .... A203742..... A203744..... A203746
Fibonacci(n+1) .. A203697..... A203699..... A203701
prime(n) ........ A203703..... A203705..... A203707
floor(n/2) ...... A203748..... A203752..... A203773
floor((n+1)/2) .. A203759..... A203763..... A203766
For f(x,y)=x^4+y^4, see A203755 and A203770. (End)

Examples

			a(4) = (1+2)*(1+3)*(1+4)*(2+3)*(2+4)*(3+4) = 12600.

References

  • Amarnath Murthy, Another combinatorial approach towards generalizing the AM-GM inequality, Octagon Mathematical Magazine, Vol. 8, No. 2, October 2000.
  • Amarnath Murthy, Smarandache Dual Symmetric Functions And Corresponding Numbers Of The Type Of Stirling Numbers Of The First Kind. Smarandache Notions Journal, Vol. 11, No. 1-2-3 Spring 2000.

Links

Crossrefs

Cf. A006963, A093884, A203469.

Programs

  • Maple
    a:= n-> mul(mul(i+j, i=1..j-1), j=2..n):
seq(a(n), n=1..12);  # Alois P. Heinz, Jul 23 2017
  • Mathematica
    f[n_] := Product[(j + k), {k, 2, n}, {j, 1, k - 1}]; Array[f, 10] (* Robert G. Wilson v, Jan 08 2013 *)
  • PARI
    A093883(n)=prod(i=1,n,(2*i-1)!/i!)  \\ M. F. Hasler, Nov 02 2012

Formula

Partial products of A006963: a(n) = Product((2*i-1)!/i!, i=1..n). - Vladeta Jovovic, May 27 2004
G.f.: G(0)/(2*x) -1/x, where G(k)= 1 + 1/(1 - 1/(1 + 1/((2*k+1)!/(k+1)!)/x/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Jun 15 2013
a(n) ~ sqrt(A/Pi) * 2^(n^2 + n/2 - 7/24) * exp(-3*n^2/4 + n/2 - 1/24) * n^(n^2/2 - n/2 - 11/24), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Jan 26 2019

Extensions

More terms from Vladeta Jovovic, May 27 2004

A203524 a(n) = Product_{2 <= i < j <= n+1} (prime(i) + prime(j)).

Original entry on oeis.org

1, 8, 960, 3870720, 535088332800, 4746447547269120000, 2251903055463146166681600000, 101133031075657891684280256430080000000, 764075218501479062478490016486870993810227200000000, 510692344365454233151092604262379676645631378616169267200000000000
Offset: 1

Views

Author

Clark Kimberling, Jan 03 2012

Keywords

Comments

Each term divides its successor, as in A203525. It is conjectured that each term is divisible by the corresponding superfactorial, A000178(n); as in A203526. See A093883 for a guide to related sequences.

Crossrefs

Cf. A000040, A203315, A203525, A203526.

Programs

  • Maple
    a:= n-> mul(mul(ithprime(i)+ithprime(j), i=2..j-1), j=3..n+1):
seq(a(n), n=1..10);  # Alois P. Heinz, Jul 23 2017
  • Mathematica
    f[j_] := Prime[j + 1]; z = 17;
v[n_] := Product[Product[f[k] + f[j], {j, 1, k - 1}], {k, 2, n}]
d[n_] := Product[(i - 1)!, {i, 1, n}]    (* A000178 *)
Table[v[n], {n, 1, z}]                   (* A203524 *)
Table[v[n + 1]/(8 v[n]), {n, 1, z - 1}]  (* A203525 *)
Table[v[n]/d[n], {n, 1, 20}]             (* A203526 *)

Extensions

Name edited by Alois P. Heinz, Jul 23 2017

A203525 a(n) = v(n+1)/(8*v(n)), where v=A203524.

Original entry on oeis.org

1, 15, 504, 17280, 1108800, 59304960, 5613753600, 944393748480, 83547459072000, 18057977118720000, 2985679725841612800, 366843845931171840000, 71218197373471948800000, 22048551163610844364800000, 7384118713322835982417920000
Offset: 1

Views

Author

Clark Kimberling, Jan 03 2012

Keywords

Comments

See A093883 for a discussion and guide to related sequences.

Crossrefs

Cf. A000040, A093883, A203315, A203524, A203526.

Programs

  • Mathematica
    f[j_] := Prime[j + 1]; z = 17;
v[n_] := Product[Product[f[k] + f[j], {j, 1, k - 1}], {k, 2, n}]
d[n_] := Product[(i - 1)!, {i, 1, n}]    (* A000178 *)
Table[v[n], {n, 1, z}]                   (* A203524 *)
Table[v[n + 1]/(8 v[n]), {n, 1, z - 1}]  (* A203525 *)
Table[v[n]/d[n], {n, 1, 20}]             (* A203526 *)

Extensions

Definition corrected by Georg Fischer, Nov 26 2021
Showing 1-5 of 5 results.

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