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.

Previous Showing 11-20 of 49 results. Next

A166168 G.f.: exp( Sum_{n>=1} Lucas(n^2)*x^n/n ) where Lucas(n) = A000204(n).

Original entry on oeis.org

1, 1, 4, 29, 585, 34212, 5600397, 2490542953, 2968152042068, 9416588994339205, 79216509536543420965, 1762508872870620792746360, 103525263562786817866762466405, 16031370626878431551103688398524485
Offset: 0

Views

Author

Paul D. Hanna, Oct 08 2009

Keywords

Comments

Conjectured to consist entirely of integers.
The Lucas numbers (A000204) forms the logarithmic derivative of the Fibonacci numbers (A000045).
Note that Lucas(n^2) = [(1+sqrt(5))/2]^(n^2) + [(1-sqrt(5))/2]^(n^2).

Examples

			G.f.: A(x) = 1 + x + 4*x^2 + 29*x^3 + 585*x^4 + 34212*x^5 +...
log(A(x)) = x + 7*x^2/2 + 76*x^3/3 + 2207*x^4/4 + 167761*x^5/5 + 33385282*x^6/6 +...+ Lucas(n^2)*x^n/n +...
		

Crossrefs

Programs

  • Maple
    with(combinat): seq(coeff(series(exp(add((fibonacci(k^2-1)+fibonacci(k^2+1))*x^k/k,k=1..n)),x,n+1), x, n), n = 0 .. 15); # Muniru A Asiru, Dec 18 2018
  • Mathematica
    CoefficientList[Series[Exp[Sum[LucasL[n^2]*x^n/n, {n, 1, 200}]], {x, 0, 50}], x](* G. C. Greubel, May 06 2016 *)
  • PARI
    {a(n)=polcoeff(exp(sum(m=1,n,(fibonacci(m^2-1)+fibonacci(m^2+1))*x^m/m)+x*O(x^n)),n)}

Formula

a(n) = (1/n)*Sum_{k=1..n} Lucas(k^2)*a(n-k), a(0)=1.
Logarithmic derivative yields A166169.

A156171 G.f.: A(x) = exp( Sum_{n>=1} x^n/(1 - 2^n*x)^n / n ), a power series in x with integer coefficients.

Original entry on oeis.org

1, 1, 3, 11, 53, 357, 3521, 51665, 1122135, 35638903, 1639453459, 108526044099, 10298220348807, 1396920580458279, 270394562069007327, 74574294532698008703, 29276455806256470979269, 16344863466384180848085765, 12969208162308705691408055345, 14616452655308018025267503353697
Offset: 0

Views

Author

Paul D. Hanna, Feb 05 2009

Keywords

Examples

			G.f.: A(x) = 1 + x + 3*x^2 + 11*x^3 + 53*x^4 + 357*x^5 + 3521*x^6 + 51665*x^7 + 1122135*x^8 + 35638903*x^9 + 1639453459*x^10 + 108526044099*x^11 +...
such that:
log(A(x)) = Sum_{n>=1} x^n/n * (1 + 2^n*x + 4^n*x^2 +...+ 2^(n*k)*x^k +...)^n
or
log(A(x)) = x*(1 + 2*x + 4*x^2 + 8*x^3 + 16*x^4 + 32*x^5 +...) +
x^2/2*(1 + 8*x + 48*x^2 + 256*x^3 + 1280*x^4 + 6144*x^5 +...) +
x^3/3*(1 + 24*x + 384*x^2 + 5120*x^3 + 61440*x^4 + 688128*x^5 +...) +
x^4/4*(1 + 64*x + 2560*x^2 + 81920*x^3 + 2293760*x^4 + 58720256*x^5 +...) +
x^5/5*(1 + 160*x + 15360*x^2 + 1146880*x^3 + 73400320*x^4 + 4227858432*x^5 +...) +
x^6/6*(1 + 384*x + 86016*x^2 + 14680064*x^3 + 2113929216*x^4 + 270582939648*x^5 +...) +...
Explicitly,
log(A(x)) = x + 5*x^2/2 + 25*x^3/3 + 161*x^4/4 + 1441*x^5/5 + 18305*x^6/6 + 330625*x^7/7 + 8488961*x^8/8 + 309465601*x^9/9 + 16011372545*x^10/10 + 1174870185985*x^11/11 + 122233833963521*x^12/12 +...
		

Crossrefs

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Exp[Sum[x^k/(1 - 2^k*x)^k/k, {k, 1, nmax}]], {x, 0, nmax}], x] (* Vaclav Kotesovec, Oct 17 2020 *)
  • PARI
    {a(n)=polcoeff(exp(sum(m=1,n,x^m/(1-2^m*x+x*O(x^n))^m/m)),n)}

Formula

a(n) ~ c * 2^(n^2/4 + n + 1/2) / (sqrt(Pi) * n^(3/2)), where c = EllipticTheta[3, 0, 1/2] = JacobiTheta3(0,1/2) = 2.1289368272118771586694585... if n is even and c = EllipticTheta[2, 0, 1/2] = JacobiTheta2(0,1/2) = 2.1289312505130275585916134... if n is odd. - Vaclav Kotesovec, Oct 17 2020

A165937 G.f.: A(x) = exp( Sum_{n>=1} A002203(n^2)*x^n/n ).

Original entry on oeis.org

1, 2, 19, 964, 334965, 742714950, 10042408885191, 814556580116590856, 393147641272746246076745, 1123539400297807898234860367690, 18948227277012085227250633551784337179, 1881331163508674280605070386666674939623268684
Offset: 0

Views

Author

Paul D. Hanna, Oct 18 2009

Keywords

Comments

A002203 equals the logarithmic derivative of the Pell numbers (A000129).
Note that A002203(n^2) = (1+sqrt(2))^(n^2) + (1-sqrt(2))^(n^2).
Given g.f. A(x), (1-x)^(1/4) * A(x)^(1/8) is an integer series.

Examples

			G.f.: A(x) = 1 + 2*x + 19*x^2 + 964*x^3 + 334965*x^4 + 742714950*x^5 +...
log(A(x)) = 2*x + 34*x^2/2 + 2786*x^3/3 + 1331714*x^4/4 + 3710155682*x^5/5 + 60245508192802*x^6/6 + 5701755387019728962*x^7/7 +...+ A002203(n^2)*x^n/n +...
		

Crossrefs

Programs

  • PARI
    {a(n)=if(n==0,1,polcoeff(exp(sum(m=1,n,polcoeff(2*(1-x)/(1-2*x-x^2+x*O(x^(m^2))),m^2)*x^m/m)+x*O(x^(n^2))),n))}

Formula

Logarithmic derivative equals A165938.
Self-convolution of A166879.

A202518 G.f. satisfies: A(x) = exp( Sum_{n>=1} (2^n - A(x))^n * x^n/n ).

Original entry on oeis.org

1, 1, 4, 111, 12600, 5722258, 10419647136, 76124127132667, 2234758718926030048, 263964471372716219981614, 125532541357451846737479404864, 240382906462440786858510574342553910, 1852958218856132372722626702327036659515008
Offset: 0

Views

Author

Paul D. Hanna, Dec 20 2011

Keywords

Comments

Compare g.f. with: G(x) = exp(Sum_{n>=1} (2 - G(x))^n * x^n/n) = 1 + x*C(-x^2) where C(x) is the Catalan function (A000108).

Examples

			G.f.: A(x) = 1 + x + 4*x^2 + 111*x^3 + 12600*x^4 + 5722258*x^5 +...
where
log(A(x)) = (2 - A(x))*x + (2^2 - A(x))^2*x^2/2 + (2^3 - A(x))^3*x^3/3 + (2^4 - A(x))^4*x^4/4 +...
		

Crossrefs

Programs

  • PARI
    {a(n)=local(A=1+x);for(i=1,n,A=exp(sum(m=1,n,(2^m-A+x*O(x^n))^m*x^m/m)));polcoeff(A,n)}

A211892 G.f.: exp( Sum_{n>=1} 3 * Jacobsthal(n^2) * x^n/n ), where Jacobsthal(n) = A001045(n).

Original entry on oeis.org

1, 3, 12, 198, 16962, 6762210, 11473594848, 80455865485692, 2306084412391039038, 268657100633050977422322, 126765866001055606588876061400, 241678197713843578271875740922972788, 1858396158245858742065123341776166504084452
Offset: 0

Views

Author

Paul D. Hanna, Apr 24 2012

Keywords

Comments

Given g.f. A(x), note that A(x)^(1/3) is not an integer series.

Examples

			G.f.: A(x) = 1 + 3*x + 12*x^2 + 198*x^3 + 16962*x^4 + 6762210*x^5 +...
such that
log(A(x))/3 = x + 5*x^2/2 + 171*x^3/3 + 21845*x^4/4 + 11184811*x^5/5 + 22906492245*x^6/6 + 187649984473771*x^7/7 +...+ Jacobsthal(n^2)*x^n/n +...
Jacobsthal numbers begin:
A001045 = [1,1,3,5,11,21,43,85,171,341,683,1365,2731,5461,10923,21845,...].
		

Crossrefs

Cf. A231279 (Jacobsthal(n^2)).

Programs

  • PARI
    {Jacobsthal(n)=polcoeff(x/(1-x-2*x^2+x*O(x^n)),n)}
    {a(n)=polcoeff(exp(sum(k=1, n, 3*Jacobsthal(k^2)*x^k/k)+x*O(x^n)), n)}
    for(n=0, 16, print1(a(n), ", "))

Formula

G.f.: (1+x) * exp( Sum_{n>=1} 2^(n^2) * x^n/n ).
a(n) = A155200(n) + A155200(n-1).

A292500 G.f.: exp( Sum_{n>=1} [ Sum_{k>=1} (2*k-1)^n * x^k ]^n / n ).

Original entry on oeis.org

1, 1, 4, 18, 122, 1382, 26992, 967860, 59207134, 6539607238, 1225903048760, 407719392472476, 233686070341415140, 233030334505100451484, 407716349332865096406960, 1219594666823043463552070760, 6484753389847998264537623184230, 58288150472645787928029816422705798, 936721167715228772497787011017302901192, 25340260842241991639562678352357479545874188
Offset: 0

Views

Author

Paul D. Hanna, Sep 17 2017

Keywords

Comments

A060187(n,k) = Sum_{j=1..k} (-1)^(k-j) * binomial(n,k-j) * (2*j-1)^(n-1).
Note that exp( Sum_{n>=1} [ Sum_{k=0..n} A060187(n+1,k+1) * x^k ] / (1-x)^(n+1) * x^n/n ) does not yield an integer series.
Conjecture: a(n)^(1/n^2) tends to 3^(1/4). - Vaclav Kotesovec, Oct 17 2020

Examples

			G.f.: A(x) = 1 + x + 4*x^2 + 18*x^3 + 122*x^4 + 1382*x^5 + 26992*x^6 + 967860*x^7 + 59207134*x^8 + 6539607238*x^9 + 1225903048760*x^10 + 407719392472476*x^11 + 233686070341415140*x^12 + 233030334505100451484*x^13 + 407716349332865096406960*x^14 + 1219594666823043463552070760*x^15 +...
RELATED SERIES.
log(A(x)) = x + 7*x^2/2 + 43*x^3/3 + 399*x^4/4 + 6091*x^5/5 + 151255*x^6/6 + 6550307*x^7/7 + 465127199*x^8/8 + 58293976795*x^9/9 + 12191724780647*x^10/10 + 4471204259257363*x^11/11 + 2799295142330495151*x^12/12 + 3026340345288168023883*x^13/13 + 5704756586858875194533367*x^14/14 +...+ A292502(n)*x^n/n +...
The logarithm of g.f. A(x) equals the series:
log(A(x)) = Sum_{n>=1} (x + 3^n*x^2 + 5^n*x^3 +...+ (2*k-1)^n*x^k +...)^n/n,
or,
log(A(x)) = (x + 3*x^2 + 5*x^3 + 7*x^4 + 9*x^5 +...) +
(x + 3^2*x^2 + 5^2*x^3 + 7^2*x^4 + 9^2*x^5 +...)^2/2 +
(x + 3^3*x^2 + 5^3*x^3 + 7^3*x^4 + 9^3*x^5 +...)^3/3 +
(x + 3^4*x^2 + 5^4*x^3 + 7^4*x^4 + 9^4*x^5 +...)^4/4 + ...
This logarithmic series can be written using the Eulerian numbers of type B like so:
log(A(x)) = (x + x^2) / (1-x)^2 +
(x + 6*x^2 + x^3)^2 / (1-x)^6/2 +
(x + 23*x^2 + 23*x^3 + x^4)^3 / (1-x)^12/3 +
(x + 76*x^2 + 230*x^3 + 76*x^4 + x^5)^4 / (1-x)^20/4 +
(x + 237*x^2 + 1682*x^3 + 1682*x^4 + 237*x^5 + x^6)^5 / (1-x)^30/5 +
(x + 722*x^2 + 10543*x^3 + 23548*x^4 + 10543*x^5 + 722*x^6 + x^7)^6 / (1-x)^42/6 +
(x + 2179*x^2 + 60657*x^3 + 259723*x^4 + 259723*x^5 + 60657*x^6 + 2179*x^7 + x^8)^7 / (1-x)^56/7 +...+
[ Sum_{k=0..n} A060187(n+1,k+1) * x^k ]^n / (1-x)^(n^2+n) * x^n/n +...
		

Crossrefs

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[Exp[Sum[2^(k^2) * x^k * LerchPhi[x, -k, 1/2]^k/k, {k, 1, nmax}]], {x, 0, nmax}], x] (* Vaclav Kotesovec, Oct 17 2020 *)
  • PARI
    {a(n) = polcoeff( exp( sum(m=1, n+1, sum(k=1, n+1, (2*k-1)^m * x^k +x*O(x^n))^m/m ) ), n)}
    for(n=0, 30, print1(a(n), ", "))
    
  • PARI
    {A060187(n, k) = sum(j=1, k, (-1)^(k-j) * binomial(n, k-j) * (2*j-1)^(n-1))}
    {a(n) = my(A=1, Oxn=x*O(x^n));
    A = exp( sum(m=1,n+1, sum(k=0, m, A060187(m+1, k+1)*x^k)^m /(1-x +Oxn)^(m^2+m) * x^m/m ) );
    polcoeff(A, n)}
    for(n=0, 30, print1(a(n), ", "))

Formula

G.f.: exp( Sum_{n>=1} [ Sum_{k=0..n} A060187(n+1,k+1) * x^k ]^n / (1-x)^(n^2+n) * x^n/n ), where A060187 are the Eulerian numbers of type B.

A156631 G.f.: A(x) = Sum_{n>=0} ( Sum_{k>=1} (2^n*2^k*x)^k/k )^n / n!, a power series in x with integer coefficients.

Original entry on oeis.org

1, 4, 64, 3072, 466944, 283115520, 814634500096, 10734635101192192, 601470215201514061824, 138785509787119430915850240, 130376354694095237162362352959488
Offset: 0

Views

Author

Paul D. Hanna, Feb 12 2009

Keywords

Comments

Compare to these dual g.f.s:
Sum_{n>=0} ( Sum_{k>=1} (2^n*x)^k/k )^n/n! (A060690);
Sum_{n>=0} ( Sum_{k>=1} (2^k*x)^k/k )^n/n! (A155200);
which, when expanded as power series in x, have only integer coefficients.

Examples

			G.f.: A(x) = 1 + 4*x + 64*x^2 + 3072*x^3 + 466944*x^4 + 283115520*x^5 + ...
From _Paul D. Hanna_, Mar 10 2009: (Start)
Let B(x) be the g.f. of A155200:
B(x) = 1 + 2*x + 10*x^2 + 188*x^3 + 16774*x^4 + 6745436*x^5 + ...
then a(n) is the coefficient of x^n in B(x)^(2^n):
B(x)^(2^0): [(1),2,10,188,16774,6745436,11466849412,...];
B(x)^(2^1): [1,(4),24,416,34400,13561728,22961051392,...];
B(x)^(2^2): [1,8,(64),1024,72704,27418624,46032420864,...];
B(x)^(2^3): [1,16,192,(3072),165888,56131584,92513894400,...];
B(x)^(2^4): [1,32,640,12288,(466944),118751232,186897137664,...];
B(x)^(2^5): [1,64,2304,65536,2129920,(283115520),382143037440,...];
B(x)^(2^6): [1,128,8704,425984,17956864,1140850688,(814634500096),...];
the terms along the diagonal (in parentheses) form this sequence. (End)
		

Crossrefs

Programs

  • PARI
    {a(n)=polcoeff(sum(j=0,n,sum(k=1, n, (2^(j+k)*x)^k/k+x*O(x^n))^j/j!),n)}
    
  • PARI
    /* a(n) = [x^n] B(x)^(2^n) where B(x) is g.f. of A155200: */ {a(n)=polcoeff(exp( 2^n*sum(k=1,n, 2^(k^2)*x^k/k)+x*O(x^n)), n)} \\ Paul D. Hanna, Mar 11 2009

Formula

a(n) = [x^n] B(x)^(2^n) where B(x) = exp(Sum_{n>=1} 2^(n^2)*x^n/n) is the g.f. of A155200. - Paul D. Hanna, Mar 10 2009

A158096 G.f.: A(x) = exp( Sum_{n>=1} x^n/n * 2^(n^2)/(1 + 2^(n^2)*x^n) ).

Original entry on oeis.org

1, 2, 6, 188, 16614, 6744492, 11466697660, 80444371592472, 2306003921102413254, 268654794307394089145676, 126765597337037378441876059252, 241678070947171631269022075304755208, 1858395916567280733577643964109494506976348, 57560683587055569906379529978030563771752589955832
Offset: 0

Views

Author

Paul D. Hanna, Mar 26 2009

Keywords

Comments

Compare to g.f. of A010054:
exp( Sum_{n>=1} x^n/(1 + x^n)/n ) = 1 + x + x^3 + x^6 + x^10 +...

Examples

			G.f.: A(x) = 1 + 2*x + 6*x^2 + 188*x^3 + 16614*x^4 + 6744492*x^5 +...
where
log(A(x)) = 2/(1 + 2*x)*x + 2^4/(1 + 2^4*x^2)*x^2/2 + 2^9/(1 + 2^9*x^3)*x^3/3 + 2^16/(1 + 2^16*x^4)*x^4/4 + 2^25/(1 + 2^25*x^5)*x^5/5 +...
Explicitly,
log(A(x)) = 2*x + 8*x^2/2 + 536*x^3/3 + 64960*x^4/4 + 33554592*x^5/5 + 68718964352*x^6/6 + 562949953422208*x^7/7 +...+ A262826(n)*x^n/n +...
		

Crossrefs

Programs

  • PARI
    {a(n)=if(n==0,1,polcoeff(exp(sum(k=1,n, x^k/k * 2^(k^2)/(1 + 2^(k^2)*x^k +x*O(x^n)))),n))}
    for(n=0,20,print1(a(n),", "))
    
  • PARI
    {a(n) = polcoeff( exp( sum(m=1, n, x^m/m * sumdiv(m, d, -(-1)^d * 2^(m^2/d) * d) ) +x*O(x^n)), n)}
    for(n=0,20,print1(a(n),", ")) \\ Paul D. Hanna, Oct 02 2015

Formula

G.f.: exp( Sum_{n>=1} x^n/n * Sum_{d|n} -(-1)^d * 2^(n^2/d) * d ). - Paul D. Hanna, Oct 02 2015
Logarithmic derivative equals A262826.

A162580 G.f.: A(x) = exp( 2*Sum_{n>=1} 2^[A007814(n)^2] * x^n/n ), where A007814(n) = exponent of highest power of 2 dividing n.

Original entry on oeis.org

1, 2, 4, 6, 16, 26, 44, 62, 240, 418, 756, 1094, 2544, 3994, 6556, 9118, 32352, 55586, 99492, 143398, 330000, 516602, 845900, 1175198, 3452112, 5729026, 9953556, 14178086, 31076592, 47975098, 77547580, 107120062, 298608832, 490097602
Offset: 0

Views

Author

Paul D. Hanna, Jul 06 2009

Keywords

Examples

			G.f.: A(x) = 1 + 2*x + 4*x^2 + 6*x^3 + 16*x^4 + 26*x^5 + 44*x^6 + ...
log(A(x))/2 = 2^0*x + 2^1*x^2 + 2^0*x^3/3 + 2^4*x^4/4 + 2^0*x^5/5 + 2^1*x^6/6 + 2^0*x^7/7 + 2^9*x^8/8 + ... + 2^[A007814(n)^2]*x^n/n + ...
		

Crossrefs

Programs

  • Mathematica
    nmax = 500; a[n_]:= SeriesCoefficient[Series[Exp[ Sum[2^(IntegerExponent[k, 2]^2 + 1)*q^k/k, {k, 1, nmax}]], {q,0,nmax}], n]; Table[a[n], {n, 0, 50}] (* G. C. Greubel, Jul 04 2018 *)
  • PARI
    {a(n)=local(L=sum(m=1,n,2*2^(valuation(m,2)^2)*x^m/m)+x*O(x^n));polcoeff(exp(L),n)}

A162582 G.f.: A(x) = exp( 2*Sum_{n>=1} A006519(n)^n * x^n/n ), where A006519(n) = highest power of 2 dividing n.

Original entry on oeis.org

1, 2, 6, 10, 146, 282, 826, 1370, 4204986, 8408602, 25223066, 42037530, 615687706, 1189337882, 3483938586, 5778539290, 2305851850537847066, 4611703695297154842, 13835111074334385946, 23058518453371617050
Offset: 0

Views

Author

Paul D. Hanna, Jul 06 2009

Keywords

Examples

			G.f.: A(x) = 1 + 2*x + 6*x^2 + 10*x^3 + 146*x^4 + 282*x^5 + 826*x^6 + ...
log(A(x))/2 = 2^0*x + 2^2*x^2 + 2^0*x^3/3 + 2^8*x^4/4 + 2^0*x^5/5 + 2^6*x^6/6 + 2^0*x^7/7 + 2^24*x^8/8 + ... + A006519(n)^n*x^n/n + ...
		

Crossrefs

Programs

  • Mathematica
    nmax = 200; a[n_]:= SeriesCoefficient[Series[Exp[ Sum[2^(k*IntegerExponent[k, 2] + 1)*q^k/k, {k, 1, nmax}]], {q,0,nmax}], n]; Table[a[n], {n,0,50}] (* G. C. Greubel, Jul 04 2018 *)
  • PARI
    {a(n)=local(L=sum(m=1,n,2*(2^valuation(m,2))^m*x^m/m)+x*O(x^n));polcoeff(exp(L),n)}
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