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 1-8 of 8 results.

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)).

A078140 Convolutory inverse of signed lower Wythoff sequence.

Original entry on oeis.org

1, 3, 5, 9, 17, 30, 52, 90, 154, 262, 446, 758, 1285, 2176, 3683, 6230, 10533, 17803, 30085, 50831, 85873, 145063, 245037, 413891, 699082, 1180761, 1994293, 3368302, 5688920, 9608292, 16227841, 27407792, 46289925, 78180465, 132041227
Offset: 1

Views

Author

Clark Kimberling, Nov 23 2002

Keywords

Comments

Suppose that r is a real number in the interval [3/2, 5/3). Let C(r) = (c(k)) be the sequence of coefficients in the Maclaurin series for 1/(Sum_{k>=0} floor((k+1)*r))(-x)^k). It appears that c(k) > 0 for all k >= 0. Indeed, it appears that C(r) is strictly increasing and that the limit L(r) of c(k+1)/c(k) as k -> oo exists. Following is a guide for selected numbers r.
** r ** C(r) L(r)
sqrt(7/3) A188135 A288238
sqrt(5/2) A288230 A288240
(1 + sqrt(5))/2 A078140 A281112
sqrt(8/3) A288233 A288935
-1 + sqrt(7) A288234 A289003
-4/5 + sqrt(6) A288236 A289032
sqrt(11/4) A288237 A289033

Examples

			a(5) = 17 = -[w(5)*a(1)-w(4)*a(2)+w(3)*a(3)-w(2)*a(4)] = -8*1+6*3-4*5+3*9. (a(1),a(2),...,a(n))(*)(w(1),-w(2),w(3),...,-d*w(n)) = (1,0,0,...,0), where (*) denotes convolution, w = lower Wythoff sequence, A000201.
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[1/Sum[Floor[GoldenRatio*(k + 1)] (-x)^k, {k, 0, 50}],
    {x, 0,50}], x]  (* Clark Kimberling, Dec 12 2016 *)

Formula

a(n) = d*[w(n)*a(1)-w(n-1)*a(2)+...+d*w(2)*a(n-1)], where d=(-1)^n, with a(1)=1 and w=floor(n*tau), tau=(1+sqrt(5))/2.

Extensions

Comments added by Clark Kimberling, Jul 10 2017

A111529 Row 2 of table A111528.

Original entry on oeis.org

1, 1, 4, 22, 148, 1156, 10192, 99688, 1069168, 12468208, 157071424, 2126386912, 30797423680, 475378906432, 7793485765888, 135284756985472, 2479535560687360, 47860569736036096, 970606394944476160, 20635652201785613824, 459015456156148876288, 10662527360021306782720
Offset: 0

Views

Author

Paul D. Hanna, Aug 06 2005

Keywords

Examples

			(1/2)*log(1 + 2*x + 6*x^2 + ... + ((n+1)!/1!)*x^n + ...)
= x + (4/2)*x^2 + (22/3)*x^3 + (148/4)*x^4 + (1156/5)*x^5 + ...
		

Crossrefs

Cf. A111528 (table), A003319 (row 1), A111530 (row 3), A111531 (row 4), A111532 (row 5), A111533 (row 6), A111534 (diagonal).

Programs

  • Maple
    N:= 30: # to get a(0) to a(N)
    g:= 1/2*log(add((n+1)!*x^n,n=0..N+1)):
    S:= series(g,x,N+1);
    1, seq(j*coeff(S,x,j),j=0..N); # Robert Israel, Jul 10 2015
  • 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[2, n];
    Table[a[n], {n, 0, 21}] (* Jean-François Alcover, Aug 09 2018 *)
  • PARI
    {a(n)=if(n<0,0,if(n==0,1, (n/2)*polcoeff(log(sum(m=0,n,(m+1)!/1!*x^m)),n)))}

Formula

G.f.: (1/2)*log(Sum_{n >= 0} (n+1)!*x^n) = Sum_{n >= 1} a(n)*x^n/n.
G.f.: 1/(1+2*x - 3*x/(1+3*x - 4*x/(1+4*x - ... (continued fraction).
a(n) = Sum_{k = 0..n} 2^(n-k)*A089949(n,k). - Philippe Deléham, Oct 16 2006
G.f. 1/(2*x-G(0)) where G(k) = 2*x - 1 - k*x - x*(k+1)/G(k+1); G(0)=x (continued fraction, Euler's 1st kind, 1-step). - Sergei N. Gladkovskii, Aug 14 2012
G.f.: 1/(2*x) - 1/(G(0) - 1) where G(k) = 1 + x*(k+1)/(1 - 1/(1 + 1/G(k+1)));(continued fraction, 3-step). - Sergei N. Gladkovskii, Nov 20 2012
G.f.: 1 + x/(G(0)-2*x) where G(k) = 1 + (k+1)*x - x*(k+3)/G(k+1); (continued fraction). - Sergei N. Gladkovskii, Dec 26 2012
G.f.: (1 + 1/Q(0))/2, where Q(k) = 1 + k*x - x*(k+2)/Q(k+1); (continued fraction). In general, the g.f. for row (r+2) is (r + 1 + 1/Q(0))/(r + 2). - Sergei N. Gladkovskii, May 04 2013
G.f.: W(0), where W(k) = 1 - x*(k+1)/( x*(k+1) - 1/(1 - x*(k+3)/( x*(k+3) - 1/W(k+1) ))); (continued fraction). - Sergei N. Gladkovskii, Aug 26 2013
a(n) ~ n! * n^2/2 * (1 - 1/n - 2/n^2 - 8/n^3 - 52/n^4 - 436/n^5 - 4404/n^6 - 51572/n^7 - 683428/n^8 - 10080068/n^9 - 163471284/n^10), where the coefficients are given by (n+2)*(n+1)/n^2 * Sum_{k>=0} A260491(k)/(n+2)^k. - Vaclav Kotesovec, Jul 27 2015
a(n) = -A077607(n+2)/2. - Vaclav Kotesovec, Jul 29 2015
From Peter Bala, Jul 12 2022: (Start)
O.g.f: A(x) = ( Sum_{k >= 0} ((k+2)!/2!)*x^k )/( Sum_{k >= 0} (k+1)!*x^k ).
A(x)/(1 - 2*x*A(x)) = Sum_{k >= 0} ((k+2)!/2!)*x^k.
Riccati differential equation: x^2*A'(x) + 2*x*A^2(x) - (1 + x)*A(x) + 1 = 0.
Apply Stokes 1982 to find that A(x) = 1/(1 - x/(1 - 3*x/(1 - 2*x/(1 - 4*x/(1 - 3*x/(1 - 5*x/(1 - ... - n*x/(1 - (n+2)*x/(1 - ...))))))))), a continued fraction of Stieltjes type. (End)

A225127 Convolutory inverse of the nonprimes.

Original entry on oeis.org

1, -4, 10, -24, 59, -146, 360, -886, 2182, -5376, 13244, -32624, 80364, -197968, 487672, -1201319, 2959297, -7289859, 17957662, -44236464, 108971015, -268436517, 661259918, -1628931424, 4012669610, -9884711639, 24349755585, -59982589144, 147759635098
Offset: 1

Views

Author

Clark Kimberling, Apr 29 2013

Keywords

Comments

Coefficients in 1/(1+g(x)), where g is the generating functions of the sequence of nonprimes: (1,4,6,8,9,...). For the convolutory inverse of the primes, see A030018. Conjecture: a(n+1)/a(n) has a limit, -2.4633754095588889..., analogous to the Backhouse constant.
The sequences with nonzero first term form a group under convolution. The identity is (1,0,0,0,...), and the inverse of a sequence r(1), r(2), r(3), ... is s(1), s(2), s(3),... given by s(1) = 1/r(1) and s(n) = -(r(2)*s(n-1) + ... + r(n)*s(1))/r(1). Thus, s(i) are the coefficients of the power series for 1/(r(1) + r(2)*x + r(3)*x^2 + ... ).

Examples

			(1,4,6,8,9,...)**(1,-4,10,-24,59,...) = (1,0,0,0,0,...), where ** denotes convolution.
		

Crossrefs

Programs

  • Mathematica
    z = 1000; c = Complement[Range[z], Prime[Range[PrimePi[z]]]]; r[n_] := r[n] = c[[n]]; k[n_] := k[n] = 0; k[1] = 1; a[n_] := a[n] = (k[n] - Sum[r[i]*a[n - i + 1], {i, 2, n}])/r[1]; t = Table[a[n], {n, 1, 40}]   (* A225127 *)

A296617 Expansion of 1/Sum_{k>=0} (k+1)^(k+1)*x^k.

Original entry on oeis.org

1, -4, -11, -104, -1388, -22980, -446524, -9882944, -244592124, -6684031040, -199824449532, -6488250797312, -227456440349948, -8565880619584896, -345018776767586572, -14805421633750610240, -674514253891722861612, -32522567276377571337728
Offset: 0

Views

Author

Seiichi Manyama, Dec 19 2017

Keywords

Crossrefs

Programs

  • PARI
    N=66; x='x+O('x^N); Vec(1/sum(k=0, N, (k+1)^(k+1)*x^k))

A303671 a(n) = [x^n] (6 / Sum_{k=0..n} (k+3)!*x^k)^(1/2).

Original entry on oeis.org

1, -2, -4, -20, -140, -1192, -11656, -127072, -1517480, -19624400, -272656064, -4046157472, -63844717184, -1067307017600, -18846094327360, -350578477836160, -6854465726916640, -140564170444594880, -3017526392523529600, -67690323794750627200
Offset: 0

Views

Author

Seiichi Manyama, Apr 28 2018

Keywords

Crossrefs

Programs

  • Maple
    [seq(coeff(series((factorial(3)/add(factorial(k+3)*x^k,k=0..n))^(1/2), x,30),x,n),n=0..25)]; # Muniru A Asiru, Apr 29 2018
  • PARI
    N=66; x='x+O('x^N); Vec((3!/sum(k=0, N, (k+3)!*x^k))^(1/2))

A303672 a(n) = [x^n] (5040 / Sum_{k=0..n} (k+7)!*x^k)^(1/4).

Original entry on oeis.org

1, -2, -8, -60, -600, -7152, -96456, -1430544, -22933920, -393013280, -7144207808, -137001926144, -2760226854816, -58242464679360, -1283886660610560, -29506641823939200, -705788634473952000, -17544801385483584000, -452659831142363014400
Offset: 0

Views

Author

Seiichi Manyama, Apr 28 2018

Keywords

Crossrefs

Programs

  • Maple
    [seq(coeff(series((factorial(7)/add(factorial(k+7)*x^k,k=0..n))^(1/4), x,30),x,n),n=0..25)]; # Muniru A Asiru, Apr 29 2018
  • PARI
    N=66; x='x+O('x^N); Vec((7!/sum(k=0, N, (k+7)!*x^k))^(1/4))

A303673 a(n) = [x^n] (15! / Sum_{k=0..n} (k+15)!*x^k)^(1/8).

Original entry on oeis.org

1, -2, -16, -204, -3264, -60384, -1239912, -27591408, -655324704, -16443029408, -432731364992, -11882079044992, -339084517212576, -10026995732141760, -306530743192692480, -9669854410016300160, -314315622535266332160
Offset: 0

Views

Author

Seiichi Manyama, Apr 28 2018

Keywords

Crossrefs

Programs

  • Maple
    [seq(coeff(series((factorial(15)/add(factorial(k+15)*x^k,k=0..n))^(1/8), x,30),x,n),n=0..25)]; # Muniru A Asiru, Apr 29 2018
  • PARI
    N=66; x='x+O('x^N); Vec((15!/sum(k=0, N, (k+15)!*x^k))^(1/8))
Showing 1-8 of 8 results.