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.

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A090365 Shifts 1 place left under the INVERT transform of the BINOMIAL transform of this sequence.

Original entry on oeis.org

1, 1, 3, 11, 47, 225, 1177, 6625, 39723, 251939, 1681535, 11764185, 86002177, 655305697, 5193232611, 42726002123, 364338045647, 3215471252769, 29331858429241, 276224445794785, 2682395337435723, 26832698102762435, 276221586866499839, 2923468922184615897
Offset: 0

Views

Author

Paul D. Hanna, Nov 26 2003

Keywords

Comments

The Hankel transform of this sequence is A000178(n+1); example: det([1,1,3; 1,3,11; 3,11,47]) = 12. - Philippe Deléham, Mar 02 2005
a(n) appears to be the number of indecomposable permutations (A003319) of [n+1] that avoid both of the dashed patterns 32-41 and 41-32. - David Callan, Aug 27 2014
This is true: A nonempty permutation avoids 32-41 and 41-32 if and only if all its components do so. So if A(x) denotes the g.f. for indecomposable {32-41,41-32}-avoiders, then F(x):=1/(1-A(x)) is the g.f. for all {32-41,41-32}-avoiders. From A074664, F(x)=1/x(1-1/B(x)) where B(x) is the o.g.f. for the Bell numbers. Solve for A(x). - David Callan, Jul 21 2017
The Hankel transform of this sequence without the a(0)=1 term is also A000178(n+1). - Michael Somos, Oct 02 2024

Crossrefs

Programs

  • Maple
    bintr:= proc(p) proc(n) add(p(k) *binomial(n,k), k=0..n) end end:
    invtr:= proc(p) local b;
               b:= proc(n) option remember; local i;
                    `if`(n<1, 1, add(b(n-i) *p(i-1), i=1..n+1))
                   end;
            end:
    b:= invtr(bintr(a)):
    a:= n-> `if`(n<0, 0, b(n-1)):
    seq(a(n), n=0..30);  # Alois P. Heinz, Jun 28 2012
  • Mathematica
    a[n_] := Module[{A, B}, A = 1+x; For[k=1, k <= n, k++, B = (A /. x -> x/(1 - x))/(1-x) + O[x]^n // Normal; A = 1 + x*A*B]; SeriesCoefficient[A, {x, 0, n}]]; Table[a[n], {n, 0, 23}] (* Jean-François Alcover, Oct 23 2016, adapted from PARI *)
  • PARI
    {a(n)=local(A); if(n<0,0,A=1+x+x*O(x^n); for(k=1,n,B=subst(A,x, x/(1-x))/(1-x)+x*O(x^n); A=1+x*A*B);polcoeff(A,n,x))}

Formula

G.f.: A(x) satisfies A(x) = 1/(1 - A(x/(1-x))*x/(1-x) ).
a(n) = Sum_{k = 0..n} A085838(n, k). - Philippe Deléham, Jun 04 2004
G.f.: 1/x-1-1/(B(x)-1) where B(x) = g.f. for A000110 the Bell numbers. - Vladeta Jovovic, Aug 08 2004
a(n) = Sum_{k=0..n} A094456(n,k). - Philippe Deléham, Nov 07 2007
G.f.: 1/(1-x/(1-2x/(1-x/(1-3x/(1-x/(1-4x/(1-x/(1-5x/(1-... (continued fraction). - Paul Barry, Feb 25 2010
From Sergei N. Gladkovskii, Jan 06 2012 - May 12 2013: (Start)
Continued fractions:
G.f.: 1 - x/(G(0)+x); G(k) = x - 1 + x*k + x*(x-1+x*k)/G(k+1).
G.f.: 1/x - 1/2 + (x^2-4)/(4*U(0)-2*x^2+8) where U(k) = k*(2*k+3)*x^2 + x - 2 - (2-x+2*k*x)*(2+3*x+2*k*x)*(k+1)*x^2/U(k+1).
G.f.: 1/x+1/(U(0)-1) where U(k) = -x*k + 1 - x - x^2*(k+1)/U(k+1).
G.f.: (1 - U(0))/x - 1 where U(k) = 1 - x*(k+2) - x^2*(k+1)/U(k+1).
G.f.: (1 - U(0))/x where U(k) = 1 - x*(k+1)/(1-x/U(k+1)).
G.f.: 1/x + 1/( G(0)-1) where G(k) = 1 - x/(1 - x*(2*k+1)/(1 - x/(1 - x*(2*k+2)/ G(k+1) ))).
G.f.:1/x + 1/( G(0) - 1 ) where G(k) = 1 - x/(1 - x*(k+1)/G(k+1) ).
G.f.: (1 - Q(0))/x where Q(k) = 1 + x/(x*k - 1 )/Q(k+1).
G.f.: 1/x - 1/x/Q(0), where Q(k) = 1 + x/(1 - x + x*(k+1)/(x - 1/Q(k+1))).
(End)
Conjecture: a(n) = b(2^(n-1) - 1) for n > 0 with a(0) = 1 where b(n) = b((n - 2^f(n))/2) + b(floor((2n - 2^f(n))/2)) + b(A025480(n-1)) for n > 0 with b(0) = 1 and where f(n) = A007814(n). - Mikhail Kurkov, Jan 11 2022

A104981 Column 1 of triangle A104980; also equals column 0 of triangle A104986, which equals the matrix logarithm of A104980.

Original entry on oeis.org

0, 1, 2, 7, 33, 191, 1297, 10063, 87669, 847015, 8989301, 103996703, 1303132269, 17589153719, 254509227541, 3931158238735, 64573130459613, 1124144767682215, 20677664894412965, 400760695386194687, 8163539437728923181
Offset: 0

Views

Author

Paul D. Hanna, Apr 10 2005

Keywords

Crossrefs

Programs

  • Mathematica
    T[n_, k_]:= T[n, k]= If[nJean-François Alcover, Aug 09 2018 *)
  • PARI
    {a(n) = if(n<0, 0, (matrix(n+2, n+2, m, j, if(m==j, 1, if(m==j+1, -m+1, -polcoeff((1-1/sum(i=0, m, i!*x^i))/x +O(x^m), m-j-1))))^-1)[n+1,2])}
    
  • Sage
    @CachedFunction
    def T(n,k):
        if (k<0 or k>n): return 0
        elif (k==n): return 1
        elif (k==n-1): return n
        else: return k*T(n, k+1) + sum( T(j, 0)*T(n, j+k+1) for j in (0..n-k-1) )
    [T(n,1) for n in (0..30)] # G. C. Greubel, Jun 07 2021

Formula

From Gary W. Adamson, Jul 14 2011: (Start)
Let M = triangle A128175 as an infinite square production matrix (deleting the first "1"):
1, 1, 0, 0, 0, ...
2, 2, 1, 0, 0, ...
4, 4, 3, 1, 0, ...
8, 8, 7, 4, 1, ...
...
a(n) = sum of top row terms of M^(n-1). Example: top row of M^4 = (71, 71, 38, 10, 1), sum = 191 = a(5). (End)
a(0) = 1, a(n) = n * a(n-1) + Sum_{j=1..n} A003319(j) * a(n - j), with offset 0 for the term 1. - F. Chapoton, Feb 26 2018

A111534 Main diagonal of table A111528.

Original entry on oeis.org

1, 1, 4, 33, 416, 7045, 149472, 3804353, 112784896, 3812791581, 144643185600, 6081135558817, 280510445260800, 14080668974435141, 763890295406672896, 44529851124925034625, 2775373003913373810688, 184147301185264051623181
Offset: 0

Views

Author

Paul D. Hanna, Aug 06 2005

Keywords

Comments

For n>0, a(n) is divisible by n: a(n)/n = A111535(n).

Crossrefs

Cf: A111528 (table), A003319 (row 1), A111529 (row 2), A111530 (row 3), A111531 (row 4), A111532 (row 5), A111533 (row 6).

Programs

  • Mathematica
    T[n_, k_] := T[n, k] = Which[n<0 || k<0, 0, k==0 || k==1, 1, n==0, k!, True, (T[n-1, k+1]-T[n-1, k])/n - Sum[T[n, j] T[n-1, k-j], {j, 1, k-1}]];
    a[n_] := T[n, n];
    Table[a[n], {n, 0, 17}] (* Jean-François Alcover, Aug 09 2018 *)
  • PARI
    {a(n)=if(n<0,0,if(n==0,1, polcoeff(log(sum(m=0,n,(n-1+m)!/(n-1)!*x^m)),n)))}

Formula

a(n) = [x^n] Log( Sum_{m=0..n} (n-1+m)!/(n-1)!*x^m ).

A112354 Inverse Euler transform of n!. Also the number of sequences of permutations with no global descents which are Lyndon (smallest in lexicographic order of all cyclic shifts of the sequences) where the size of the sequence = sum of sizes of the permutations.

Original entry on oeis.org

1, 1, 4, 17, 92, 572, 4156, 34159, 314368, 3199844, 35703996, 433421495, 5687955724, 80256874912, 1211781887796, 19496946534720, 333041104402860, 6019770246910128, 114794574818830716, 2303332661416242633, 48509766592884311132, 1069983257387132347080
Offset: 1

Views

Author

Mike Zabrocki, Sep 05 2005

Keywords

Examples

			a(3) = 4 because (123), (213), (132) and (1,21) are all Lyndon.
a(4) = 17 because there are 13 permutations with no global descents of size 4 and (1,123), (1,213), (1,132) are all Lyndon.
a(5) = 92 = 71 permutations with no global descents+13 sequences of the form (1,pi) where pi in S_4 with no global descents+(1,1,1,21),(1,21,21),(1,1,123),(1,1,213),(1,1,132),(21,123),(21,213),(21,132).
		

Crossrefs

Programs

  • Maple
    read transforms; EULERi([seq(n!,n=1..30)]);
    # The function EulerInvTransform is defined in A358451.
    a := EulerInvTransform(factorial):
    seq(a(n), n = 1..22); # Peter Luschny, Nov 21 2022
  • Mathematica
    ff = Range[n = 22]!; s = {}; For[i = 1, i <= n, i++, AppendTo[s, i*ff[[i]] - Sum[s[[d]]*ff[[i-d]], {d, i-1}]]]; Table[Sum[If[Divisible[i, d], MoebiusMu[i/d], 0]*s[[d]], {d, 1, i}]/i, {i, n}] (* Jean-François Alcover, Apr 15 2016 *)

Formula

Product_{k>=1} 1/(1-x^k)^{a(k)} = Sum_{n>=0} n! x^n.
a(n) ~ n! * (1 - 1/n - 1/n^2 - 4/n^3 - 23/n^4 - 171/n^5 - 1542/n^6 - 16241/n^7 - 194973/n^8 - 2622610/n^9 - 39027573/n^10 - ...), for coefficients see A113869. - Vaclav Kotesovec, Sep 04 2014, extended Nov 27 2020

A158882 G.f. A(x) satisfies: [x^n] A(x)^n = [x^n] A(x)^(n-1) for n>1 with A(0)=A'(0)=1.

Original entry on oeis.org

1, 1, -1, 3, -13, 71, -461, 3447, -29093, 273343, -2829325, 31998903, -392743957, 5201061455, -73943424413, 1123596277863, -18176728317413, 311951144828863, -5661698774848621, 108355864447215063, -2181096921557783605
Offset: 0

Views

Author

Paul D. Hanna, Apr 30 2009

Keywords

Comments

After initial term, equals signed A003319 (indecomposable permutations).

Examples

			G.f.: A(x) = 1 + x - x^2 + 3*x^3 - 13*x^4 + 71*x^5 - 461*x^6 +-...
1/A(x) = 1 - x + 2*x^2 - 6*x^3 + 24*x^4 +...+ (-1)^n*n!*x^n +...
...
Coefficients of powers of g.f. A(x) begin:
A^1: 1,1,(-1),3,-13,71,-461,3447,-29093,273343,-2829325,...;
A^2: 1,2,(-1),(4),-19,110,-745,5752,-49775,476994,-5016069,...;
A^3: 1,3, 0, (4),(-21),129,-910,7242,-64155,626319,-6685548,...;
A^4: 1,4, 2, 4, (-21),(136),-996,8152,-73811,733244,-7938186,...;
A^5: 1,5, 5, 5, -20, (136),(-1030),8650,-79925,807055,-8854741,...;
A^6: 1,6, 9, 8, -18, 132, (-1030),(8856),-83385,855010,-9500385,...;
A^7: 1,7,14,14, -14, 126, -1008, (8856),(-84861),882805,-9927890,...;
A^8: 1,8,20,24, -6, 120, -972, 8712, (-84861),(894928),-10180120,...;
A^9: 1,9,27,39,9,117,-927,8469,-83772,(894928),(-10291986),...;
A^10:1,10,35,60,35,122,-875,8160,-81890,885620,(-10291986),...; ...
where coefficients [x^n] A(x)^n and [x^n] A(x)^(n-1) are
enclosed in parenthesis and equal (-1)^n*n*A075834(n+1):
[ -1,4,-21,136,-1030,8856,-84861,894928,-10291986,128165720,...];
compare to A075834:
[1,1,1,2,7,34,206,1476,12123,111866,1143554,12816572,...]
and also to the logarithmic derivative of A075834:
[1,1,4,21,136,1030,8856,84861,894928,10291986,128165720,...].
		

Crossrefs

Cf. A003319, A075834, A159311, variant: A158883.

Programs

  • Mathematica
    b[0] = 0; b[n_] := b[n] = n!-Sum[k!*b[n-k], {k, 1, n-1}]; a[0] = 1; a[n_] := (-1)^(n+1)*b[n]; Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Mar 07 2014, from 2nd formula *)
  • Maxima
    G(n,k):=(if n=k then 1 else if k=1 then (-sum(binomial(n-1,k-1)*G(n,k),k,2,n)) else sum(G(i+1,1)*G(n-i-1,k-1),i,0,n-k));
    makelist(G(n,1),n,1,10); /* Vladimir Kruchinin, Mar 07 2014 */
  • PARI
    a(n)=polcoeff(1/sum(k=0,n,(-1)^k*k!*x^k +x*O(x^n)),n)
    
  • PARI
    {a(n)=local(A=[1,1]);for(i=2,n,A=concat(A,0);A[ #A]=(Vec(Ser(A)^(#A-2))-Vec(Ser(A)^(#A-1)))[ #A]);A[n+1]}
    

Formula

a(n) = (2-n) * a(n-1) - Sum_{k=1..n-1} a(k) * a(n-k) if n>1. - Michael Somos, Jul 23 2011
a(n) = (-1)^(n-1)*A003319(n) for n>=1.
G.f.: A(x) = 1/[Sum_{n>=0} (-1)^n*n!*x^n].
G.f. satisfies: [x^(n+1)] A(x)^n = (-1)^n*n*A075834(n+1) for n>=0.
From Sergei N. Gladkovskii, Jun 24 2012 to May 26 2013: (Start)
Continued fractions:
Let A(x) be the g.f., then A(x) = 1-x/U(0), where U(k) = x-1+x*k+(k+2)*x/U(k+1).
A(x) = 1/U(0), where U(k) = 1 - x*(2*k+1)/(1 - 2*x*(k+1)/(2*x*(k+1)- 1/U(k+1))).
G.f.: U(0), where U(k)= 1 + x*(k+1)/(1 + x*(k+1)/U(k+1)).
G.f.: 2/(G(0) + 1), where G(k)= 1 - x*(k+1)/(1 - 1/(1 + 1/G(k+1))).
G.f.: x*G(0), where G(k)=1/x + 2*k + 1 - (k+1)^2/G(k+1).
G.f.: 2/G(0), where G(k)= 1 + 1/(1 - x*(k+1)/(x*(k+1) - 1/G(k+1))). (End)

A261214 Coefficients in an asymptotic expansion of sequence A259472.

Original entry on oeis.org

1, -3, 0, -4, -33, -283, -2785, -31291, -395360, -5544754, -85427259, -1433955817, -26046643595, -509070113635, -10653941722236, -237754202827284, -5636787946661521, -141514316248243499, -3751121064314067653, -104704135027419849139, -3070176356776990397500
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 12 2015

Keywords

Examples

			A259472(n)/(-2*n!) ~ 1 - 3/n - 4/n^3 - 33/n^4 - 283/n^5 - 2785/n^6 - ...
		

Crossrefs

Programs

  • Mathematica
    Flatten[{1, Table[Sum[CoefficientList[Assuming[Element[x, Reals], Series[E^(3/x)*x^3/ExpIntegralEi[1/x]^3, {x, 0, 25}]], x][[k+1]] * StirlingS2[n-1, k-1], {k, 1, n}], {n, 1, 20}]}]

Formula

a(k) ~ -3 * k! / (4 * (log(2))^(k+1)).
For n>0, a(n) = Sum_{k=1..n} A261239(k) * Stirling2(n-1, k-1).

A261239 Coefficients in an asymptotic expansion of A259472 in falling factorials.

Original entry on oeis.org

1, -3, 0, -4, -21, -129, -910, -7242, -64155, -626319, -6685548, -77527104, -971315713, -13084909917, -188723009274, -2902997766470, -47458671376503, -821951603042523, -15037432614035864, -289828080356525052, -5870642802374608509, -124691017072423632777
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 12 2015

Keywords

Examples

			A259472(n)/(-2*n!) ~ 1 - 3/n - 4/(n*(n-1)*(n-2)) - 21/(n*(n-1)*(n-2)*(n-3)) - 129/(n*(n-1)*(n-2)*(n-3)*(n-4)) - ... [coefficients are A261239]
A259472(n)/(-2*n!) ~ 1 - 3/n - 4/n^3 - 33/n^4 - 283/n^5 - 2785/n^6 - ... [coefficients are A261214]
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Assuming[Element[x, Reals], Series[E^(3/x) * x^3 / ExpIntegralEi[1/x]^3, {x, 0, 25}]], x]

Formula

a(n) ~ -3 * n! * (1 - 4/n + 2/n^2 - 2/n^3 - 31/n^4 - 288/n^5 - 2939/n^6 - 33944/n^7 - 438614/n^8 - 6266312/n^9 - 98050303/n^10), coefficients are A261253.
For n>0, a(n) = Sum_{k=1..n} A261214(k) * Stirling1(n-1, k-1).

A261253 Coefficients in an asymptotic expansion of sequence A261239.

Original entry on oeis.org

1, -4, 2, -2, -31, -288, -2939, -33944, -438614, -6266312, -98050303, -1667563622, -30631857759, -604518210964, -12758658946466, -286833669370926, -6844757550430019, -172833310268551740, -4604828067485736507, -129123684195177403168, -3801830662346341617586
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 12 2015

Keywords

Examples

			A261239(n)/(-3*n!) ~ 1 - 4/n + 2/n^2 - 2/n^3 - 31/n^4 - 288/n^5 - 2939/n^6 - ...
		

Crossrefs

Programs

  • Mathematica
    Flatten[{1, Table[Sum[CoefficientList[Assuming[Element[x, Reals], Series[E^(4/x)*x^4/ExpIntegralEi[1/x]^4, {x, 0, 25}]], x][[k+1]] * StirlingS2[n-1, k-1], {k, 1, n}], {n, 1, 25}]}]

Formula

a(k) ~ -k! / (log(2))^(k+1).
For n>0, a(n) = Sum_{k=1..n} A261254(k) * Stirling2(n-1, k-1).

A261254 Coefficients in an asymptotic expansion of A261239 in falling factorials.

Original entry on oeis.org

1, -4, 2, -4, -21, -136, -996, -8152, -73811, -733244, -7938186, -93126716, -1178054657, -15998857056, -232339375664, -3594982133808, -59070662442383, -1027605845674036, -18873206761567638, -365015243426704372, -7416392564276075453, -157957992952546414328
Offset: 0

Views

Author

Vaclav Kotesovec, Aug 12 2015

Keywords

Examples

			A261239(n)/(-3*n!) ~ 1 - 4/n + 2/(n*(n-1)) - 4/(n*(n-1)*(n-2)) - 21/(n*(n-1)*(n-2)*(n-3)) - 136/(n*(n-1)*(n-2)*(n-3)*(n-4)) - 996/(n*(n-1)*(n-2)*(n-3)*(n-4)*(n-5)) - ... [coefficients are A261254]
A261239(n)/(-3*n!) ~ 1 - 4/n + 2/n^2 - 2/n^3 - 31/n^4 - 288/n^5 - 2939/n^6 - ... [coefficients are A261253]
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Assuming[Element[x, Reals], Series[E^(4/x) * x^4 / ExpIntegralEi[1/x]^4, {x, 0, 25}]], x]

Formula

a(n) ~ -4 * n! * (1 - 5/n + 5/n^2 - 30/n^4 - 286/n^5 - 2960/n^6 - 34890/n^7 - 459705/n^8 - 6678641/n^9 - 105999991/n^10).
For n>0, a(n) = Sum_{k=1..n} A261253(k) * Stirling1(n-1, k-1).

A049295 Number of subgroups of index 4 in free group of rank n+1.

Original entry on oeis.org

1, 71, 2143, 54335, 1321471, 31817471, 764217343, 18344733695, 440294408191, 10567189327871, 253613279903743, 6086723113107455, 146081381003558911, 3505953301484470271, 84142880178680889343, 2019429129941297135615, 48466299152487396933631
Offset: 0

Views

Author

Keywords

References

  • P. de la Harpe, Topics in Geometric Group Theory, Univ. Chicago Press, 2000, p. 23, N_{4,n}.
  • R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.13(b).

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{37,-368,1436,-2256,1152},{1,71,2143,54335,1321471},20] (* Harvey P. Dale, Apr 14 2016 *)

Formula

a(n) = 4*24^n-4*6^n-2*4^n+4*2^n-1.
G.f.: (264*x^3+116*x^2-34*x-1) / ((x-1)*(2*x-1)*(4*x-1)*(6*x-1)*(24*x-1)). [Colin Barker, Feb 17 2013]

Extensions

More terms from Carrie Westbrook (s1213407(AT)cedarville.edu)
Terms corrected by Colin Barker, May 08 2012
a(16) from Colin Barker, Feb 17 2013
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