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 1-4 of 4 results.

A144690 Limit of the coefficient of x^(2^m+n) in B(x)^(n+1) as m grows, where B(x) = Sum_{k>=0} x^(2^k).

Original entry on oeis.org

1, 2, 6, 16, 130, 636, 5712, 34336, 811458, 7151380, 113034746, 1049982792, 25276020640, 293841338896, 5712436923000, 68827002466176, 3739997267623490, 60752008945662372, 1718332635327516238, 26832922324005759560, 1099199814287516279394
Offset: 0

Views

Author

Paul D. Hanna, Oct 10 2008

Keywords

Comments

The g.f. of A144691(n) = a(n)/(n+1) appears to have an interesting functional interpretation.
For a fixed n, the sequence of [x^(2^m+n)] B(x)^(n+1), m=0,1,2,... seems to stabilize at m = n + A023416(n). [From Max Alekseyev, Dec 19 2011]

Crossrefs

Programs

  • PARI
    { a(n) = local(m=n+log(n+.5)\log(2), B=sum(k=0,m,x^(2^k)));if(n<0, 0, polcoeff((B+O(x^(2^m+n+1)))^(n+1),2^m+n)) }

Formula

a(n) = (n+1)*A144691(n).

Extensions

a(14), a(15) corrected and a(16)-a(23) added by Max Alekseyev, May 03 2011
a(24)-a(27) in b-file from Max Alekseyev, Dec 19 2011

A135068 a(n) = [x^(2^n+n-1)] (x + x^2 + x^4 + x^8 + ... + x^2^n)^n for n>=1.

Original entry on oeis.org

1, 2, 6, 16, 90, 636, 5712, 34336, 537282, 5941780, 99729146, 1049982792, 23200347040, 293841338896, 5712436923000, 68827002466176, 2844850573581890, 53069160498788772, 1545326270301621838, 26021954987946879560, 1020860369624228471394, 19905401189634441143740, 605270985059438427438138, 11141784565490367848976336, 621465511993167908247508400, 14470690420043042111787089216, 548187222712632324159956010732, 11881058908943228840652007583056
Offset: 1

Views

Author

Paul D. Hanna, Nov 17 2007

Keywords

Crossrefs

Cf. A007178 (variant); A135069, A135070 (variant), A135071.

Programs

  • Mathematica
    f[x_, n_] := (Sum[x^(2^k), {k, 0, n}])^n; Table[Coefficient[f[x, n], x^(2^n + n - 1)] , {n, 1, 20}] (* G. C. Greubel, Sep 22 2016 *)
  • PARI
    a(n)=if(n<1,0,polcoeff(sum(j=0,n,x^(2^j)+O(x^(2^n+n)))^n,2^n+n-1))

Formula

a(n) = A135069(n)*n.

Extensions

a(15)-a(19) from Alois P. Heinz, Apr 29 2009
a(20)-a(22) from Max Alekseyev, Dec 03 2010
a(23)-a(28) from Max Alekseyev, Aug 31 2024

A135069 a(n) = [x^(2^n+n-1)] (x + x^2 + x^4 + x^8 + ... + x^(2^n))^n / n for n>=1.

Original entry on oeis.org

1, 1, 2, 4, 18, 106, 816, 4292, 59698, 594178, 9066286, 87498566, 1784642080, 20988667064, 380829128200, 4301687654136, 167344151387170, 2948286694377154, 81332961594822202, 1301097749397343978, 48612398553534689114, 904790963165201870170, 26316129785192975106006, 464241023562098660374014, 24858620479726716329900336, 556565016155501619684118816, 20303230470838234228146518916, 424323532462258172880428842252
Offset: 1

Views

Author

Paul D. Hanna, Nov 17 2007

Keywords

Crossrefs

Programs

  • Mathematica
    f[x_, n_] := (1/n)*(Sum[x^(2^k), {k, 0, n}])^n; Table[Coefficient[f[x, n], x^(2^n + n - 1)] , {n, 1, 10}] (* G. C. Greubel, Sep 22 2016 *)
  • PARI
    {a(n)=if(n<1,0,polcoeff(sum(j=0,n,x^(2^j)+O(x^(2^n+n)))^n,2^n+n-1)/n)}

Formula

a(n) = A135068(n)/n for n>=1.

Extensions

a(15)-a(19) from Alois P. Heinz, Apr 29 2009
a(20)-a(22) from Max Alekseyev, Dec 03 2010
a(23)-a(28) from Max Alekseyev, Aug 31 2024

A135070 a(n) = [x^(2^n+n-2)] (x + x^2 + x^4 + x^8 + ... + x^(2^n))^n for n>=1.

Original entry on oeis.org

1, 1, 3, 18, 70, 600, 4956, 52528, 358128, 6654600, 79967800, 1453049400, 16239408120, 392541718660, 5252687631660, 108961629396480, 1395025456201408, 62831427044385384, 1223872353413404344, 37391632408971430120, 655014723078024641640, 27055523795138159291124, 547691411941958414420092, 17365164578604322437671664, 332211955074827711097949200, 19385342415197943809053622700, 466687147661484232610990714436, 18326221432646410203582181439808
Offset: 1

Views

Author

Paul D. Hanna, Nov 17 2007

Keywords

Crossrefs

Programs

  • Mathematica
    f[x_, n_] := (Sum[x^(2^k), {k, 0, n}])^n; Table[Coefficient[f[x, n], x^(2^n + n - 2)] , {n, 2, 10}] (* G. C. Greubel, Sep 22 2016 *)
  • PARI
    {a(n)=if(n<2,0,polcoeff(sum(j=0,n,x^(2^j)+O(x^(2^n+n)))^n,2^n+n-2))}

Formula

n(n-1)/2 divides a(n) for n>=2: A135071(n) = a(n)/[n(n-1)/2] for n>=2.

Extensions

a(15)-a(19) from Alois P. Heinz, Apr 29 2009
a(1) prepended and a(20)-a(28) added by Max Alekseyev, Aug 31 2024
Showing 1-4 of 4 results.