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 1-10 of 13 results. Next

A129374 G.f. satisfies: A(x) = 1/(1-x) * A(x^2)*A(x^3)*A(x^4)*...*A(x^n)*...

Original entry on oeis.org

1, 1, 2, 3, 6, 8, 15, 20, 35, 48, 76, 103, 166, 221, 333, 451, 671, 894, 1303, 1730, 2479, 3288, 4615, 6086, 8502, 11142, 15299, 20034, 27285, 35514, 47937, 62168, 83259, 107650, 142929, 184090, 243207, 312041, 409210, 523709, 683261, 871239, 1130703
Offset: 0

Views

Author

Paul D. Hanna, Apr 12 2007

Keywords

Crossrefs

Programs

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

Formula

G.f.: A(x) = Product_{n>=1} 1/(1 - x^n)^A074206(n) where A074206(n) equals the number of ordered factorizations of n.
a(n) ~ exp((1 + 1/r) * (-Gamma(1+r) * Zeta(1+r) / Zeta'(r))^(1/(1+r)) * n^(r/(1+r))) * (-Gamma(1+r) * Zeta(1+r) / Zeta'(r))^(1/(10*(1+r))) / ((2*Pi)^(29/50) * sqrt(1+r) * n^((6 + 5*r)/(10*(1+r)))), where r = A107311 = 1.7286472389981836181351... is the root of the equation Zeta(r) = 2, Zeta'(r) = -1/A247667. - Vaclav Kotesovec, Nov 04 2018

A247667 Decimal expansion of the coefficient c_m in c_m*log(N), the asymptotic mean number of factors in a random factorization of n <= N.

Original entry on oeis.org

5, 5, 0, 0, 1, 0, 0, 0, 5, 4, 1, 3, 1, 5, 4, 4, 9, 1, 8, 3, 3, 0, 5, 8, 1, 2, 6, 7, 0, 2, 2, 2, 2, 1, 9, 6, 4, 6, 1, 1, 6, 8, 2, 2, 7, 1, 0, 2, 7, 1, 4, 0, 4, 0, 9, 8, 8, 8, 3, 9, 6, 5, 8, 5, 8, 9, 2, 9, 0, 5, 3, 0, 6, 6, 6, 6, 0, 5, 6, 4, 8, 5, 9, 5, 1, 1, 8, 7, 2, 0, 6, 5, 2, 3, 5, 3, 4, 6, 6, 5, 4
Offset: 0

Views

Author

Jean-François Alcover, Sep 22 2014

Keywords

Examples

			0.55001000541315449183305812670222219646116822710271404...
		

References

  • Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.5. Kalmár’s Composition Constant, p. 293.

Crossrefs

Programs

  • Mathematica
    digits = 101; rho = x /. FindRoot[Zeta[x] == 2, {x, 2}, WorkingPrecision -> digits+5]; cm = -1/Zeta'[rho]; RealDigits[cm, 10, digits] // First

Formula

c_m = -1/zeta'(rho), where rho = 1.728647... is A107311, the real solution to zeta(rho) = 2.
Residue_{s = rho} 1/(2 - Zeta(s)). - Vaclav Kotesovec, Nov 04 2018

A129375 E.g.f. satisfies: A(x) = exp(x) * A(x^2)*A(x^3)*A(x^4)*...*A(x^n)*...

Original entry on oeis.org

1, 1, 3, 13, 97, 621, 6571, 58633, 779073, 9317017, 138628531, 1977676581, 37384244833, 620735382853, 12434855135067, 245117537189281, 5651550278494081, 123266430844431153, 3128700944169196003
Offset: 0

Views

Author

Paul D. Hanna, Apr 12 2007

Keywords

Crossrefs

Programs

  • PARI
    {a(n)=local(A=1+x);for(i=2,n,A=exp(x+x*O(x^n))*prod(n=2,i,subst(A,x,x^n+x*O(x^i)))); n!*polcoeff(A,n)}

Formula

E.g.f.: A(x) = exp( Sum_{n>=1} A074206(n)*x^n ) where A074206(n) equals the number of ordered factorizations of n.
a(n) ~ n! * exp(2/5 + (1 + 1/r) * (-Gamma(1+r) / Zeta'(r))^(1/(1+r)) * n^(r/(1+r))) * (-Gamma(1+r) / Zeta'(r))^(1/(2*(1+r))) / (sqrt(2*Pi*(1+r)) * n^((2+r)/(2*(1+r)))), where r = A107311 = 1.7286472389981836181351... is the root of the equation Zeta(r) = 2, Zeta'(r) = -1/A247667. - Vaclav Kotesovec, Nov 04 2018

Extensions

PARI program fixed by Vaclav Kotesovec, Feb 26 2014

A307605 G.f. A(x) satisfies: A(x) = (1 + x) * A(x^2)^2*A(x^3)^3*A(x^4)^4* ... *A(x^k)^k* ...

Original entry on oeis.org

1, 1, 2, 5, 12, 20, 48, 81, 169, 305, 580, 1009, 1966, 3338, 6067, 10503, 18730, 31633, 55641, 93151, 160389, 267585, 452762, 747016, 1253644, 2049943, 3390786, 5516227, 9034745, 14572790, 23668066, 37918484, 61042425, 97231826, 155292944, 245774727, 389998116
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 18 2019

Keywords

Comments

Weigh transform of A050369.

Examples

			G.f.: A(x) = 1 + x + 2*x^2 + 5*x^3 + 12*x^4 + 20*x^5 + 48*x^6 + 81*x^7 + 169*x^8 + 305*x^9 + ...
		

Crossrefs

Programs

  • Mathematica
    terms = 36; A[] = 1; Do[A[x] = (1 + x) Product[A[x^k]^k, {k, 2, terms}] + O[x]^(terms + 1) // Normal, terms + 1]; CoefficientList[A[x], x]

Formula

G.f.: Product_{k>=1} (1 + x^k)^(k*A074206(k)).
a(n) ~ ((2^(-1-r) - 1) * Gamma(2+r) * zeta(2+r) / zeta'(r))^(1/(4 + 2*r)) * exp((2+r)/(1+r) * ((2^(-1-r) - 1) * Gamma(2+r) * zeta(2+r) / zeta'(r))^(1/(2+r)) * n^((1+r)/(2+r))) / (2^(1/50) * sqrt(Pi*(2+r)) * n^((3 + r)/(4 + 2*r))), where r = A107311 is the root of the equation zeta(r) = 2. - Vaclav Kotesovec, Mar 18 2021

A304965 Expansion of Product_{k>=1} 1/(1 - x^k)^tau_k(k), where tau_k(k) = number of ordered k-factorizations of k (A163767).

Original entry on oeis.org

1, 1, 3, 6, 19, 30, 96, 152, 461, 775, 1883, 3271, 8751, 14370, 34004, 59491, 140450, 239746, 541817, 932681, 2089189, 3606641, 7719178, 13398411, 28848808, 49603982, 103047935, 179154858, 370200348, 639269735, 1295389370, 2241994088, 4511677298, 7798101800, 15408901600
Offset: 0

Views

Author

Ilya Gutkovskiy, May 22 2018

Keywords

Comments

Euler transform of A163767.

Crossrefs

Programs

  • Maple
    A:= proc(n, k) option remember; `if`(k=1, 1,
          add(A(d, k-1), d=numtheory[divisors](n)))
        end:
    a:= proc(n) option remember; `if`(n=0, 1, add(add(d*
          A(d$2), d=numtheory[divisors](j))*a(n-j), j=1..n)/n)
        end:
    seq(a(n), n=0..40);  # Alois P. Heinz, May 22 2018
  • Mathematica
    nmax = 34; CoefficientList[Series[Product[1/(1 - x^k)^Times@@(Binomial[# + k - 1, k - 1]&/@FactorInteger[k][[All, 2]]), {k, 1, nmax}], {x, 0, nmax}], x]
    a[n_] := a[n] = If[n == 0, 1, Sum[Sum[d Times@@(Binomial[# + d - 1, d - 1]&/@FactorInteger[d][[All, 2]]), {d, Divisors[k]}] a[n - k], {k, 1, n}]/n]; Table[a[n], {n, 0, 34}]

Formula

G.f.: Product_{k>=1} 1/(1 - x^k)^A163767(k).

A318767 G.f. satisfies: A(x) = (1+x)/(1-x) * A(x^2)*A(x^3)*A(x^4)*...*A(x^n)*... .

Original entry on oeis.org

1, 2, 4, 8, 16, 28, 52, 88, 152, 252, 416, 664, 1076, 1684, 2636, 4060, 6248, 9444, 14292, 21312, 31748, 46796, 68804, 100200, 145784, 210240, 302520, 432428, 616716, 873972, 1236136, 1738560, 2439936, 3407924, 4749160, 6589156, 9123976, 12582620, 17316052, 23745756
Offset: 0

Views

Author

Seiichi Manyama, Nov 04 2018

Keywords

Comments

Convolution of A129373 and A129374. - Vaclav Kotesovec, Nov 05 2018

Crossrefs

Formula

G.f.: Product_{k>=1} ((1 + x^k)/(1 - x^k))^A074206(k) where A074206(n) is the number of ordered factorizations of n.
a(n) ~ exp((1+r) * ((2^(1+r) - 1) * Gamma(1+r) * Zeta(1+r))^(1/(1+r)) * n^(r/(1+r)) / (r * 2^(r/(1+r)) * (-Zeta'(r))^(1/(1+r)))) * (-2*(2^(1+r) - 1) * Gamma(1+r) * Zeta(1+r) / Zeta'(r))^(1/(10*(1+r))) / (2^(7/25) * Pi^(29/50) * sqrt(1+r) * n^((6+5*r)/(10*(1+r)))), where r = A107311 = 1.7286472389981836181351... is the root of the equation Zeta(r) = 2, Zeta'(r) = -1/A247667. - Vaclav Kotesovec, Nov 05 2018

A308272 G.f. A(x) satisfies: A(x) = (1 + x) * A(x^2)*A(x^3)*A(x^5)* ... *A(x^prime(k))* ...

Original entry on oeis.org

1, 1, 1, 2, 2, 3, 5, 6, 7, 10, 13, 16, 22, 27, 33, 44, 53, 65, 84, 101, 124, 156, 187, 226, 280, 336, 403, 492, 587, 700, 850, 1008, 1195, 1435, 1693, 2004, 2390, 2808, 3303, 3910, 4584, 5372, 6328, 7387, 8619, 10106, 11757, 13675, 15961, 18508, 21464, 24948, 28845, 33345
Offset: 0

Views

Author

Ilya Gutkovskiy, May 17 2019

Keywords

Comments

Weigh transform of A008480.

Crossrefs

Programs

  • Maple
    g:= proc(n) option remember; (l-> add(i, i=l)!/
          mul(i!, i=l))(map(i-> i[2], ifactors(n)[2]))
        end:
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
          add(binomial(g(i), j)*b(n-i*j, i-1), j=0..n/i)))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..60);  # Alois P. Heinz, May 17 2019
  • Mathematica
    terms = 53; A[] = 1; Do[A[x] = (1 + x) Product[A[x^Prime[k]], {k, 1, terms}] + O[x]^(terms + 1) // Normal, terms + 1]; CoefficientList[A[x], x]

Formula

G.f.: Product_{k>=1} (1 + x^k)^A008480(k).

A308284 G.f. A(x) satisfies: A(x) = (1 + x) * A(x^3)*A(x^5)*A(x^7)* ... *A(x^(2*k-1))* ...

Original entry on oeis.org

1, 1, 0, 1, 1, 1, 1, 1, 2, 3, 3, 2, 4, 4, 4, 7, 8, 7, 9, 10, 11, 15, 15, 16, 23, 26, 24, 32, 36, 37, 47, 51, 54, 66, 71, 79, 99, 105, 108, 132, 148, 156, 184, 203, 219, 262, 282, 297, 358, 390, 417, 484, 531, 569, 654, 718, 773, 888, 962, 1037, 1198, 1303, 1390, 1592, 1740, 1868
Offset: 0

Views

Author

Ilya Gutkovskiy, May 18 2019

Keywords

Crossrefs

Programs

  • Mathematica
    terms = 65; A[] = 1; Do[A[x] = (1 + x) Product[A[x^(2 k - 1)], {k, 2, terms}] + O[x]^(terms + 1) // Normal, terms + 1]; CoefficientList[A[x], x]

Formula

G.f.: Product_{k>=1} (1 + x^(2*k-1))^A074206(2*k-1).

A321317 G.f. satisfies: A(x) = (1-x) * A(x^2)*A(x^3)*A(x^4)*...*A(x^n)*... .

Original entry on oeis.org

1, -1, -1, 0, -1, 2, -1, 3, -1, 1, 4, -2, -4, -1, 7, -11, 0, -6, 3, -6, 9, 2, -6, 2, 5, 12, -16, 48, 4, -1, -28, 26, -30, 30, -62, 12, 16, -55, -9, -39, 18, -47, 103, -149, 87, -182, 210, -9, 45, 75, 225, -174, 39, 273, 11, 164, -224, 77, -105, 117, -703, 715, -678
Offset: 0

Views

Author

Seiichi Manyama, Nov 04 2018

Keywords

Crossrefs

Convolution inverse of A129374.

Formula

G.f.: Product_{k>=1} (1 - x^k)^A074206(k) where A074206(n) is the number of ordered factorizations of n.

A321325 G.f. satisfies: A(x) = (1 + x) * Product_{k>0} A(x^(2*k)) / Product_{k>1} A(x^(2*k-1)).

Original entry on oeis.org

1, 1, 1, 0, 1, 0, 0, -2, 2, 1, 2, -3, 1, -3, -1, -7, 8, 4, 9, -7, 7, -7, 0, -21, 15, 2, 18, -23, 8, -25, -1, -43, 46, 17, 58, -34, 40, -41, 9, -98, 79, 10, 100, -98, 40, -123, -2, -191, 176, 43, 237, -136, 144, -192, 30, -362, 277, 12, 373, -314, 131, -457, -9, -606
Offset: 0

Views

Author

Seiichi Manyama, Nov 05 2018

Keywords

Crossrefs

Formula

G.f.: Product_{k>0} (1 + x^k)^A067856(k).
Product_{k>0} A(x^k) = Product_{k>=0} (1 + x^(2^k))^(2^k). (Cf. A073707.)
Showing 1-10 of 13 results. Next