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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A000189 Number of solutions to x^3 == 0 (mod n).

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 1, 4, 3, 1, 1, 2, 1, 1, 1, 4, 1, 3, 1, 2, 1, 1, 1, 4, 5, 1, 9, 2, 1, 1, 1, 8, 1, 1, 1, 6, 1, 1, 1, 4, 1, 1, 1, 2, 3, 1, 1, 4, 7, 5, 1, 2, 1, 9, 1, 4, 1, 1, 1, 2, 1, 1, 3, 16, 1, 1, 1, 2, 1, 1, 1, 12, 1, 1, 5, 2, 1, 1, 1, 4, 9, 1, 1, 2, 1, 1, 1, 4, 1, 3
Offset: 1

Views

Author

Keywords

Comments

Shadow transform of the cubes A000578. - Michel Marcus, Jun 06 2013

Examples

			a(4) = 2 because 0^3 == 0, 1^3 == 1, 2^3 == 0, and 3^3 == 3 (mod 4); also, a(9) = 3 because 0^3 = 0, 3^3 == 0, and 6^3 = 0 (mod 9), while x^3 =/= 0 (mod 9) for x = 1, 2, 4, 5, 7, 8. - _Petros Hadjicostas_, Sep 16 2019
		

Crossrefs

Programs

  • Mathematica
    Array[ Function[ n, Count[ Array[ PowerMod[ #, 3, n ]&, n, 0 ], 0 ] ], 100 ]
    f[p_, e_] := p^Floor[2*e/3]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 19 2020 *)
  • PARI
    a(n)=my(f=factor(n));prod(i=1,#f[,1],f[i,1]^(2*f[i,2]\3)) \\ Charles R Greathouse IV, Jun 06 2013
    
  • PARI
    for(n=1, 100, print1(direuler(p=2, n, (1 + X + p*X^2)/(1 - p^2*X^3))[n], ", ")) \\ Vaclav Kotesovec, Aug 30 2021

Formula

Multiplicative with a(p^e) = p^[2e/3]. - David W. Wilson, Aug 01 2001
a(n) = n/A019555(n). - Petros Hadjicostas, Sep 15 2019
Dirichlet g.f.: zeta(3*s-2) * Product_{p prime} (1 + 1/p^s + 1/p^(2*s-1)). - Amiram Eldar, Sep 09 2023
From Vaclav Kotesovec, Sep 09 2023: (Start)
Dirichlet g.f.: zeta(s) * zeta(2*s-1) * zeta(3*s-2) * Product_{p prime} (1 - 1/p^(2*s) - 1/p^(3*s-1) - 1/p^(4*s-2) + 1/p^(4*s-1) + 1/p^(5*s-2)).
Let f(s) = Product_{primes p} (1 - 1/p^(2*s) - 1/p^(3*s-1) - 1/p^(4*s-2) + 1/p^(4*s-1) + 1/p^(5*s-2)).
Sum_{k=1..n} a(k) ~ (f(1)*n/6) * (log(n)^2/2 + (6*gamma - 1 + f'(1)/f(1))*log(n) + 1 - 6*gamma + 11*gamma^2 - 14*sg1 + (6*gamma - 1)*f'(1)/f(1) + f''(1)/(2*f(1))), where
f(1) = Product_{primes p} (1 - 3/p^2 + 2/p^3) = A065473 = 0.2867474284344787341078927127898384464343318440970569956414778593366522431...,
f'(1) = f(1) * Sum_{primes p} 9*log(p) / (p^2 + p - 2) = f(1) * 4.1970213428422788650375569145777616746065054412058004220013841318980729375...,
f''(1) = f'(1)^2/f(1) + f(1) * Sum_{primes p} (-29*p^2 - 17*p + 1) * log(p)^2 / (p^2 + p - 2)^2 = f'(1)^2/f(1) + f(1) * (-21.3646716550082193262514333696570765444176783899223644201265894338042468...),
gamma is the Euler-Mascheroni constant A001620 and sg1 is the first Stieltjes constant (see A082633). (End)

A061502 a(n) = Sum_{k<=n} tau(k)^2, where tau = number of divisors function A000005.

Original entry on oeis.org

1, 5, 9, 18, 22, 38, 42, 58, 67, 83, 87, 123, 127, 143, 159, 184, 188, 224, 228, 264, 280, 296, 300, 364, 373, 389, 405, 441, 445, 509, 513, 549, 565, 581, 597, 678, 682, 698, 714, 778, 782, 846, 850, 886, 922, 938, 942, 1042, 1051, 1087
Offset: 1

Views

Author

N. J. A. Sloane, Jun 14 2001

Keywords

References

  • R. Ayoub, An Introduction to the Analytic Theory of Numbers, Amer. Math. Soc., 1963; Chapter II, Problem 56.

Crossrefs

Programs

  • Magma
    [&+[NumberOfDivisors(k^2)*Floor(n/k): k in [1..n]]: n in [1..60]]; // Vincenzo Librandi, Sep 10 2016
  • Mathematica
    Table[Sum[DivisorSigma[0, k^2]*Floor[n/k], {k, 1, n}], {n, 1, 50}] (* Vaclav Kotesovec, Aug 30 2018 *)
    Accumulate[Table[DivisorSigma[0, n]^2, {n, 1, 50}]] (* Vaclav Kotesovec, Sep 10 2018 *)
  • PARI
    for (n=1, 1024, write("b061502.txt", n, " ", sum(k=1, n, numdiv(k)^2)) ) \\ Harry J. Smith, Jul 23 2009
    
  • PARI
    vector(60, n, sum(k=1, n, numdiv(k)^2)) \\ Michel Marcus, Jul 23 2015
    
  • PARI
    first(n)=my(v=vector(n),s); forfactored(k=1,n, v[k[1]] = s += numdiv(k)^2); v; \\ Charles R Greathouse IV, Nov 28 2018
    

Formula

a(n) = Sum_{k=1..n} tau(k^2)*floor(n/k).
Asymptotic to A*n*log(n)^3 + B*n*log(n)^2 + C*n*log(n) + D*n + O(n^(1/2+eps)) where A = 1/Pi^2 and B = (12*gamma-3)/Pi^2 - 36*zeta'(2)/Pi^4. [corrected by Vaclav Kotesovec, Aug 30 2018]
C = 36*gamma^2/Pi^2 - (288*z1/Pi^4 + 24/Pi^2)*gamma + (864*z1^2/Pi^6 + 72*z1/Pi^4 - 72/Pi^4*z2 + 6/Pi^2) - 24*g1/Pi^2 and D = 24*gamma^3/Pi^2 - (432*z1 /Pi^4+ 36/Pi^2)*gamma^2 + (3456*z1^2/Pi^6 + 288*(z1-z2)/Pi^4 + 24/Pi^2 - 72*g1/Pi^2)*gamma + g1*(288*z1/Pi^4 + 24/Pi^2)-10368*z1^3/Pi^8 - 864*z1^2/Pi^6 + 1728*z2*z1/Pi^6 + 72*(z2-z1)/Pi^4- 48*z3/Pi^4 + (12*g2-6)/Pi^2, where gamma is the Euler-Mascheroni constant A001620, z1 = Zeta'(2) = A073002, z2 = Zeta''(2) = A201994, z3 = Zeta'''(2) = A201995 and g1, g2 are the Stieltjes constants, see A082633 and A086279. - Vaclav Kotesovec, Sep 10 2018
See Cully-Hugill & Trudgian, Theorem 2, for an explicit version of the asymptotic given above. - Charles R Greathouse IV, Nov 19 2019

Extensions

Definition corrected by N. J. A. Sloane, May 25 2008

A055155 a(n) = Sum_{d|n} gcd(d, n/d).

Original entry on oeis.org

1, 2, 2, 4, 2, 4, 2, 6, 5, 4, 2, 8, 2, 4, 4, 10, 2, 10, 2, 8, 4, 4, 2, 12, 7, 4, 8, 8, 2, 8, 2, 14, 4, 4, 4, 20, 2, 4, 4, 12, 2, 8, 2, 8, 10, 4, 2, 20, 9, 14, 4, 8, 2, 16, 4, 12, 4, 4, 2, 16, 2, 4, 10, 22, 4, 8, 2, 8, 4, 8, 2, 30, 2, 4, 14, 8, 4, 8, 2, 20, 17, 4, 2, 16, 4, 4, 4, 12, 2, 20, 4, 8, 4, 4
Offset: 1

Views

Author

Leroy Quet, Jul 02 2000

Keywords

Comments

a(n) is odd iff n is odd square. - Vladeta Jovovic, Aug 27 2002
From Robert Israel, Dec 26 2015: (Start)
a(n) >= A000005(n), with equality iff n is squarefree (i.e., is in A005117).
a(n) = 2 iff n is prime. (End)

Examples

			a(9) = gcd(1,9) + gcd(3,3) + gcd(9,1) = 5, since 1, 3, 9 are the positive divisors of 9.
		

Crossrefs

Programs

  • Maple
    N:= 1000: # to get a(1) to a(N)
    V:= Vector(N):
    for k from 1 to N do
       for j from 1 to floor(N/k) do
         V[k*j]:= V[k*j]+igcd(k,j)
       od
    od:
    convert(V,list); # Robert Israel, Dec 26 2015
  • Mathematica
    Table[DivisorSum[n, GCD[#, n/#] &], {n, 94}] (* Michael De Vlieger, Sep 23 2017 *)
    f[p_, e_] := If[EvenQ[e], (p^(e/2)*(p+1)-2)/(p-1), 2*(p^((e+1)/2)-1)/(p-1)]; a[1] = 1; a[n_] := Times @@ (f @@@ FactorInteger[n]); Array[a, 100] (* Amiram Eldar, Sep 30 2020 *)
  • PARI
    a(n) = sumdiv(n, d, gcd(d, n/d)); \\ Michel Marcus, Aug 03 2016
    
  • Python
    from sympy import divisors, gcd
    def A055155(n): return sum(gcd(d,n//d) for d in divisors(n,generator=True)) # Chai Wah Wu, Aug 19 2021

Formula

Multiplicative with a(p^e) = (p^(e/2)*(p+1)-2)/(p-1) for even e and a(p^e) = 2*(p^((e+1)/2)-1)/(p-1) for odd e. - Vladeta Jovovic, Nov 01 2001
Dirichlet g.f.: (zeta(s))^2*zeta(2s-1)/zeta(2s); inverse Mobius transform of A000188. - R. J. Mathar, Feb 16 2011
Dirichlet convolution of A069290 and A008966. - R. J. Mathar, Oct 31 2011
Sum_{k=1..n} a(k) ~ 3*n / (2*Pi^6) * (Pi^4 * log(n)^2 + ((8*g - 2)*Pi^4 - 24 * Pi^2 * z1) * log(n) + 2*Pi^4 * (1 - 4*g + 5*g^2 - 6*sg1) + 288 * z1^2 - 24 * Pi^2 * (-z1 + 4*g*z1 + z2)), where g is the Euler-Mascheroni constant A001620, sg1 is the first Stieltjes constant A082633, z1 = Zeta'(2) = A073002, z2 = Zeta''(2) = A201994. - Vaclav Kotesovec, Feb 01 2019
a(n) = (1/n)*Sum_{i=1..n} sigma(gcd(n,i^2)). - Ridouane Oudra, Dec 30 2020
a(n) = Sum_{k=1..n} gcd(gcd(n,k),n/gcd(n,k))/phi(n/gcd(n,k)), where phi = A000010. - Richard L. Ollerton, May 09 2021

A086281 Decimal expansion of 4th Stieltjes constant gamma_4.

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, Jul 14 2003

Keywords

Examples

			0.0023253...
		

References

  • Steven R. Finch, Mathematical Constants, Cambridge, 2003, p. 166.

Crossrefs

Programs

  • Mathematica
    Join[{0, 0}, RealDigits[ N[ -StieltjesGamma[4], 103]][[1]]] (* Jean-François Alcover, Nov 07 2012 *)

Formula

Using the abbreviations a = log(z^2 + 1/4)/2, b = arctan(2*z) and c = cosh(Pi*z) then gamma_4 = -(Pi/5)*Integral_{0..infinity} (a^5-10*a^3*b^2+5*a*b^4)/c^2. The general case is for n>=0 (which includes Euler's gamma as gamma_0) gamma_n = (-Pi/ (n+1))*Integral_{0..infinity} sigma(n+1)/c^2, where sigma(n) = Sum_{k=0.. floor(n/2)}(-1)^k*binomial(n,2*k)*b^(2*k)*a^(n-2*k). - Peter Luschny, Apr 19 2018

A086282 Decimal expansion of 5th Stieltjes constant gamma_5.

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, Jul 14 2003

Keywords

Examples

			0.00079332381730106270175333487744444483...
		

References

  • Steven R. Finch, Mathematical Constants, Cambridge, 2003, p. 166.

Crossrefs

Programs

A183141 Decimal expansion of 6th Stieltjes constant, negated.

Original entry on oeis.org

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

Views

Author

Paul Muljadi, Feb 01 2011

Keywords

Examples

			-0.000238769345430199609872421841908004277783715156358....
		

Crossrefs

Programs

  • Maple
    evalf(gamma(6)); # R. J. Mathar, Feb 02 2011
  • Mathematica
    RealDigits[StieltjesGamma[6], 10, 100][[1]]

A183167 Decimal expansion of 7th Stieltjes constant, negated.

Original entry on oeis.org

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

Views

Author

Paul Muljadi, Feb 01 2011

Keywords

Examples

			-0.000527289567057751046074097505478858281996253472969895...
		

Crossrefs

Programs

  • Maple
    evalf(gamma(7)) ; # R. J. Mathar, Feb 02 2011
  • Mathematica
    Join[{0, 0, 0}, RealDigits[StieltjesGamma[7], 10, 100][[1]]] (* Alonso del Arte, Feb 01 2011 *)

A183206 Decimal expansion of 8th Stieltjes constant, negated.

Original entry on oeis.org

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

Views

Author

Paul Muljadi, Feb 01 2011

Keywords

Examples

			-0.00035212335380303950960205216500120874172918053379235....
		

Crossrefs

Programs

  • Maple
    evalf(gamma(8)) ;
  • Mathematica
    RealDigits[StieltjesGamma[8], 10, 100][[1]] (* Alonso del Arte, Feb 01 2011 *)

A184853 Decimal expansion of 9th Stieltjes constant, negated.

Original entry on oeis.org

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

Views

Author

Paul Muljadi, Feb 01 2011

Keywords

Examples

			-0.000034394774418088048177914623798227390620789538594442....
		

Crossrefs

Programs

  • Maple
    evalf(gamma(9)); # R. J. Mathar, Feb 02 2011
  • Mathematica
    Join[{0, 0, 0, 0}, RealDigits[ N[ -StieltjesGamma[9], 101]][[1]]] (* Jean-François Alcover, Nov 07 2012 *)

A184854 Decimal expansion of 10th Stieltjes constant.

Original entry on oeis.org

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

Views

Author

Paul Muljadi, Feb 01 2011

Keywords

Examples

			0.00020533281490906479468372228923706530295985377416676....
		

References

  • Steven R. Finch, "Stieltjes Constants." Section 2.21 in Mathematical Constants. Cambridge: Cambridge University Press (2003), 166 - 171.

Crossrefs

Programs

  • Mathematica
    RealDigits[StieltjesGamma[10], 10, 100][[1]] (* Alonso del Arte, Feb 01 2011 *)
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