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.

A052186 Number of permutations of [n] with no strong fixed points.

Original entry on oeis.org

1, 0, 1, 3, 14, 77, 497, 3676, 30677, 285335, 2928846, 32903721, 401739797, 5298600772, 75092880273, 1138261010851, 18378421938366, 314928827507717, 5708689036074089, 109145365739197964, 2195167574579322013, 46331767712354136479, 1023970009016490622478
Offset: 0

Views

Author

N. J. A. Sloane, Feb 04 2000

Keywords

Comments

A strong fixed point is a fixed point (or splitter) p(k)=k such that p(i) < k for i < k and p(j) > k for j > k.
Equals INVERTi transform of the factorials, n starting with 0. Triangle A144108 has row sums = n! with left border = A052186. - Gary W. Adamson, Sep 11 2008

References

  • Stanley, R. P., Enumerative Combinatorics, Volume 1 (1986), p. 49

Crossrefs

Cf. A144108, A000142. - Gary W. Adamson, Sep 11 2008
Column k=0 of A186373.

Programs

  • Maple
    t1 := add(n!*x^n, n=0..100): F := series(t1/(1+x*t1), x, 100): for i from 0 to 20 do printf(`%d, `, coeff(F, x, i)) od: # Zerinvary Lajos, Mar 22 2009
    # second Maple program:
    a:= proc(n) a(n):= -`if`(n<0, 1, add(a(n-i-1)*i!, i=0..n)) end:
    seq(a(n), n=0..25);  # Alois P. Heinz, May 21 2013
  • Mathematica
    m = 20; CoefficientList[ Series[ 1 / (x + 1/Sum[ n!*x^n, {n, 0, m}]), {x, 0, m}], x] (* Jean-François Alcover, Aug 30 2011, after Michael Somos *)
    nmax = 25; Rest[CoefficientList[Assuming[Element[x, Reals], Series[-1/(ExpIntegralEi[1/x]/E^(1/x) + 1), {x, 0, nmax+1}]], x]] (* Vaclav Kotesovec, Aug 05 2015 *)
  • PARI
    {a(n)=if(n<0, 0, polcoeff( 1/ (x+1/sum(k=0, n, k!*x^k, x*O(x^n))), n))} /* Michael Somos, Oct 11 2006 */

Formula

G.f.: F(x)/(1 + x*F(x)), F(x) = Sum_{n >= 0} n!*x^n.
a(0)=1, a(1)=0, a(n) = (n-2)*a(n-1) + Sum_{k=0..n-1} a(k)*a(n-1-k) + Sum_{k=0..n-2} a(k)*a(n-2-k) if n > 1. - Michael Somos, Oct 11 2006
G.f.: 1/(1-x^2/(1-3x-4x^2/(1-5x-9x^2/(1-7x-16x^2/(1-9x-25x^2/(1-... (continued fraction). - Paul Barry, Dec 09 2009
If p[i] = Stirling1(i,1) and if A is the Hessenberg matrix of order n defined by A[i,j] = p[j-i+1], (i <= j), A[i,j] = -1, (i=j+1), and A[i,j]=0 otherwise, then, for n >= 1, a(n-1) = (-1)^(n-1) det A. - Milan Janjic, May 08 2010
From Gary W. Adamson, Jul 22 2011: (Start)
a(n) = upper left term in (-1)*M^(n+1), M = an infinite square production matrix in which a column of (-1)'s is prepended to Pascal's triangle as follows:
-1, 1, 0, 0, 0, 0, ...
-1, 1, 1, 0, 0, 0, ...
-1, 1, 2, 1, 0, 0, ...
-1, 1, 3, 3, 1, 0, ...
-1, 1, 4, 6, 4, 1, ...
... (End)
G.f.: A(x) = 1/(1/G(0) + x); G(k) = 1 + x*(2*k+1)/(1 - 2*x*(k+1)/(2*x*(k+1) + 1/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Dec 29 2011
G.f.: A(x) = 1/x = 1/(1+x)*(1+x/((1+x)*G(0)-x)); G(k) = 1 + x*(k+1) - x*(k+2)/G(k+1); (continued fraction Euler's kind, 1-step ). - Sergei N. Gladkovskii, Dec 29 2011
G.f.: 1/(G(0) + x) where G(k) = 1 - x*(k+1)/(1 - x*(k+1)/G(k+1) ); (recursively defined continued fraction). - Sergei N. Gladkovskii, Dec 19 2012
G.f.: 1/(1 - W(0)) where W(k) = x*(2*k+1) - 1 - x^2*(k+1)^2/W(k+1); (recursively defined continued fraction). - Sergei N. Gladkovskii, Dec 19 2012
G.f.: 1/(G(0) + x), where G(k)= 1 + x*k - x*(k+1)/G(k+1); (continued fraction). - Sergei N. Gladkovskii, Jul 03 2013
a(n) ~ n! * (1 - 2/n + 1/n^2 - 1/n^3 - 9/n^4 - 59/n^5 - 474/n^6 - 4560/n^7 - 50364/n^8 - 625385/n^9 - 8622658/n^10), for coefficients see A256168. - Vaclav Kotesovec, Mar 16 2015
a(n) = n! - Sum_{k=0..n-1} (n-k-1)!*a(k). - Pontus von Brömssen, Jul 10 2021
a(n) + A006932(n) = n!. - Pontus von Brömssen, Jul 10 2021

Extensions

Better description from James Sellers, Mar 13 2000

A260503 Coefficients in an asymptotic expansion of sequence A003319.

Original entry on oeis.org

1, -2, -1, -5, -32, -253, -2381, -25912, -319339, -4388949, -66495386, -1100521327, -19751191053, -382062458174, -7924762051957, -175478462117633, -4132047373455024, -103115456926017761, -2718766185148876961, -75529218928863243200, -2205316818199975235447
Offset: 0

Views

Author

Vaclav Kotesovec, Jul 27 2015

Keywords

Examples

			A003319(n) / n! ~ 1 - 2/n - 1/n^2 - 5/n^3 - 32/n^4 - 253/n^5 - 2381/n^6 - ...
		

Crossrefs

Programs

  • Mathematica
    Flatten[{1, Table[Sum[Assuming[Element[x,Reals], SeriesCoefficient[E^(2/x)*x^2 / ExpIntegralEi[1/x]^2,{x,0,k}]] * StirlingS2[n-1,k-1], {k,1,n}], {n,1,20}]}] (* Vaclav Kotesovec, Aug 03 2015 *)

Formula

a(k) ~ -k! / (2 * (log(2))^(k+1)).
For n>0, Sum_{k=1..n} a(k) * Stirling1(n-1, k-1) = A259472(n). - Vaclav Kotesovec, Aug 03 2015
For n>0, a(n) = Sum_{k=1..n} A259472(k) * Stirling2(n-1, k-1). - Vaclav Kotesovec, Aug 03 2015

A260578 Coefficients in asymptotic expansion of sequence A259869.

Original entry on oeis.org

1, 0, -2, -6, -29, -196, -1665, -16796, -194905, -2549468, -37055681, -592013436, -10307671769, -194225544124, -3937581243201, -85460277981116, -1977127315636969, -48573021658496348, -1262954975286604673, -34650561545808167292, -1000438355724912080873
Offset: 0

Views

Author

Vaclav Kotesovec, Jul 29 2015

Keywords

Comments

For k > 1 is a(k) negative.

Examples

			A259869(n) / (n!/exp(1)) ~ 1 - 2/n^2 - 6/n^3 - 29/n^4 - 196/n^5 - 1665/n^6 - ...
		

Crossrefs

Programs

  • Mathematica
    nmax = 20; b = CoefficientList[Assuming[Element[x, Reals], Series[x^2*E^(2 + 2/x)/ExpIntegralEi[1 + 1/x]^2, {x, 0, nmax}]], x]; Flatten[{1, Table[Sum[b[[k+1]]*StirlingS2[n-1, k-1], {k, 1, n}], {n, 1, nmax}]}] (* Vaclav Kotesovec, Aug 03 2015 *)

Formula

a(k) ~ -k! / (2 * exp(1) * (log(2))^(k+1)).

A260491 Coefficients in asymptotic expansion of sequence A077607.

Original entry on oeis.org

1, -4, 0, -8, -76, -752, -8460, -107520, -1522124, -23717424, -402941324, -7407988448, -146479479308, -3099229422352, -69863683041868, -1671667534710720, -42318672085310540, -1130167625049525232, -31758424368739424780, -936840101208573355680
Offset: 0

Views

Author

Vaclav Kotesovec, Jul 27 2015

Keywords

Comments

For k > 2 is a(k) negative.

Examples

			A077607(n) / (-n!) ~ 1 - 4/n - 8/n^3 - 76/n^4 - 752/n^5 - 8460/n^6 - ...
		

Crossrefs

Programs

  • Mathematica
    nmax = 30; b = CoefficientList[Assuming[Element[x, Reals], Series[x^4*E^(2/x)/(ExpIntegralEi[1/x] - x*E^(1/x))^2, {x, 0, nmax}]], x]; Flatten[{1, Table[Sum[b[[k+1]]*StirlingS2[n-1, k-1], {k, 1, n}], {n, 1, nmax}]}] (* Vaclav Kotesovec, Aug 03 2015 *)

Formula

a(k) ~ -k * k! / (4 * (log(2))^(k+2)).

A260532 Coefficients in asymptotic expansion of sequence A051295.

Original entry on oeis.org

1, 2, 7, 31, 165, 1025, 7310, 59284, 543702, 5618267, 65200918, 846462826, 12229783811, 195394019337, 3427472046792, 65526442181293, 1355785469986828, 30166624979467869, 717769036033944699, 18174105506247664633, 487655384740384445407, 13816406622559942660420
Offset: 0

Views

Author

Vaclav Kotesovec, Jul 28 2015

Keywords

Examples

			A051295(n)/(n-1)! ~ 1 + 2/n + 7/n^2 + 31/n^3 + 165/n^4 + 1025/n^5 + 7310/n^6 + ...
		

Crossrefs

Programs

  • Mathematica
    nmax = 30; b = CoefficientList[Assuming[Element[x, Reals], Series[E^(2/x)*x / (ExpIntegralEi[1/x] - E^(1/x))^2, {x, 0, nmax+1}]], x]; Table[Sum[b[[k+1]] * StirlingS2[n, k-1], {k, 1, n+1}], {n, 0, nmax}] (* Vaclav Kotesovec, Aug 03 2015 *)

Formula

a(k) ~ 2 * (k-1)! / (log(2))^k.
a(n) = Sum_{k=0..n} A134378(k) * Stirling2(n, k). - Vaclav Kotesovec, Aug 04 2015

A260530 Coefficients in asymptotic expansion of sequence A051296.

Original entry on oeis.org

1, 2, 7, 35, 216, 1575, 13243, 126508, 1359437, 16312915, 217277446, 3194459333, 51557948291, 908431129702, 17376289236947, 358847480175063, 7959468559605624, 188702262366570387, 4760773506835189975, 127312428854513811012, 3596091234340397964321
Offset: 0

Views

Author

Vaclav Kotesovec, Jul 28 2015

Keywords

Examples

			A051296(n) / n! ~ 1 + 2/n + 7/n^2 + 35/n^3 + 216/n^4 + 1575/n^5 + 13243/n^6 + ...
		

Crossrefs

Programs

  • Mathematica
    nmax = 30; b = CoefficientList[Assuming[Element[x, Reals], Series[E^(2/x)*x^2 / (ExpIntegralEi[1/x] - 2*x*E^(1/x))^2, {x, 0, nmax}]], x]; Flatten[{1, Table[Sum[b[[k+1]]*StirlingS2[n-1, k-1], {k, 1, n}], {n, 1, nmax}]}] (* Vaclav Kotesovec, Aug 03 2015 *)

Formula

a(k) ~ k! / (2 * (log(2))^(k+1)).

A201684 a(n) = 2*A052186(n) - n!.

Original entry on oeis.org

1, -1, 0, 0, 4, 34, 274, 2312, 21034, 207790, 2228892, 25890642, 324477994, 4370180744, 63007469346, 968847653702, 15834053988732, 274170226919434, 5015004366420178, 96645631069563928, 1957433140982004026
Offset: 0

Views

Author

N. J. A. Sloane, Dec 03 2011

Keywords

Crossrefs

Formula

a(n) ~ n! * (1 - 4/n + 2/n^2 - 2/n^3 - 18/n^4 - 118/n^5 - 948/n^6 - 9120/n^7 - 100728/n^8 - 1250770/n^9 - 17245316/n^10), for coefficients see 2*A256168. - Vaclav Kotesovec, Mar 17 2015

A260957 Coefficients in asymptotic expansion of sequence A225960.

Original entry on oeis.org

1, -1, 0, 2, 11, 97, 1105, 13905, 189633, 2803873, 44875599, 774931369, 14385283720, 286010393240, 6069158797378, 137001560841500, 3279733485742038, 83029219746406610, 2216965307395350215, 62282348739259200015, 1836840301301564071196, 56750954571528670989664
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 05 2015

Keywords

Examples

			A225960(n)/(2*(n-1)!) ~ 1 - 1/n + 2/n^3 + 11/n^4 + 97/n^5 + 1105/n^6 + ...
		

Crossrefs

Formula

a(k) ~ k! / (2 * (log(2))^(k+1)). - Vaclav Kotesovec, Aug 05 2015

A305275 Coefficients in asymptotic expansion of sequence A302557.

Original entry on oeis.org

1, 0, 2, 6, 35, 256, 2187, 21620, 243947, 3098528, 43799819, 682540780, 11630529643, 215190967544, 4296657514283, 92083313483300, 2108244638675035, 51350077108834832, 1325682930813985547, 36157047428501464220, 1038793351537388253211, 31354977545074731373512
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 18 2018

Keywords

Examples

			A302557(n) / (exp(-1) * n!) ~ 1 + 2/n^2 + 6/n^3 + 35/n^4 + 256/n^5 + 2187/n^6 + ...
		

Crossrefs

Formula

a(k) ~ k! / (2 * exp(1) * (log(2))^(k+1)).
Showing 1-9 of 9 results.