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 1-9 of 9 results.

A085158 Sextuple factorials, 6-factorials, n!!!!!!, n!6.

Original entry on oeis.org

1, 1, 2, 3, 4, 5, 6, 7, 16, 27, 40, 55, 72, 91, 224, 405, 640, 935, 1296, 1729, 4480, 8505, 14080, 21505, 31104, 43225, 116480, 229635, 394240, 623645, 933120, 1339975, 3727360, 7577955, 13404160, 21827575, 33592320, 49579075, 141639680
Offset: 0

Views

Author

Hugo Pfoertner, Jun 21 2003

Keywords

Comments

The term "Sextuple factorial numbers" is also used for the sequences A008542, A008543, A011781, A047058, A047657, A049308, which have a different definition. The definition given here is the one commonly used.

Examples

			a(14) = 224 because 14*a(14-6) = 14*a(8) = 14*16 = 224.
		

Crossrefs

Cf. n!:A000142, n!!:A006882, n!!!:A007661, n!!!!:A007662, n!!!!!:A085157, 6-factorial primes: n!!!!!!+1:A085150, n!!!!!!-1:A051592.
Cf. A288093.

Programs

  • GAP
    a:= function(n)
        if n<1 then return 1;
        else return n*a(n-6);
        fi;
      end;
    List([0..40], n-> a(n) ); # G. C. Greubel, Aug 21 2019
  • Magma
    b:=func< n | n le 6 select n else n*Self(n-6) >;
    [1] cat [b(n): n in [1..40]]; // G. C. Greubel, Aug 21 2019
    
  • Maple
    a:= n-> `if`(n<1, 1, n*a(n-6)); seq(a(n), n=0..40); # G. C. Greubel, Aug 21 2019
  • Mathematica
    Table[Times@@Range[n,1,-6],{n,0,40}] (* Harvey P. Dale, Aug 10 2019 *)
  • PARI
    a(n)=if(n<1, 1, n*a(n-6));
    vector(40, n, n--; a(n) ) \\ G. C. Greubel, Aug 21 2019
    
  • Sage
    def a(n):
        if (n<1): return 1
        else: return n*a(n-6)
    [a(n) for n in (0..40)] # G. C. Greubel, Aug 21 2019
    

Formula

a(n)=1 for n < 1, otherwise a(n) = n*a(n-6).
Sum_{n>=0} 1/a(n) = A288093. - Amiram Eldar, Nov 10 2020

A143280 Decimal expansion of m(2) = Sum_{n>=0} 1/n!!.

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, Aug 04 2008

Keywords

Comments

Also decimal expansion of Sum_{n>=1} n!!/n!. - Michel Lagneau, Dec 24 2011
Apart from the first digit, the same as A227569. - Robert G. Wilson v, Apr 09 2014

Examples

			3.05940740534257614453947549923327861297725472633534020929971877980544281968...
		

Crossrefs

Cf. A227569.
Cf. A006882 (n!!), this sequence (m(2)), A288055 (m(3)), A288091 (m(4)), A288092 (m(5)), A288093 (m(6)), A288094 (m(7)), A288095 (m(8)), A288096 (m(9)).

Programs

  • Magma
    SetDefaultRealField(RealField(100)); R:= RealField(); Exp(1/2)*(1 + Sqrt(Pi(R)/2)*Erf(1/Sqrt(2) )); // G. C. Greubel, Mar 27 2019
    
  • Mathematica
    RealDigits[ Sqrt[E] + Sqrt[E*Pi/2]*Erf[1/Sqrt[2]], 10, 105][[1]] (* or *)
    RealDigits[ Sum[1/n!!, {n, 0, 125}], 10, 105][[1]] (* Robert G. Wilson v, Apr 09 2014 *)
    RealDigits[Total[1/Range[0,200]!!],10,120][[1]] (* Harvey P. Dale, Apr 10 2022 *)
  • PARI
    default(realprecision, 100); exp(1/2)*(1 + sqrt(Pi/2)*(1-erfc(1/sqrt(2) ))) \\ G. C. Greubel, Mar 27 2019
    
  • Sage
    numerical_approx(exp(1/2)*(1 + sqrt(pi/2)*erf(1/sqrt(2))), digits=100) # G. C. Greubel, Mar 27 2019

Formula

Equals sqrt(e) + sqrt((e*Pi)/2)*erf(1/sqrt(2)).

A288055 Decimal expansion of m(3) = Sum_{n>=0} 1/n!!!, the 3rd reciprocal multifactorial constant.

Original entry on oeis.org

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

Views

Author

Jean-François Alcover, Jun 05 2017

Keywords

Examples

			3.298913538088419003401217808261469769077803695683207090885045129...
		

Crossrefs

Cf. A007661 (n!!!), A143280 (m(2)), this sequence (m(3)), A288091 (m(4)), A288092 (m(5)), A288093 (m(6)), A288094 (m(7)), A288095 (m(8)), A288096 (m(9)).

Programs

  • Magma
    SetDefaultRealField(RealField(100)); (Exp(1/3)/3)*(3 + 3^(1/3)*Gamma(1/3, 1/3) + 3^(2/3)*Gamma(2/3, 1/3)); // G. C. Greubel, Mar 27 2019
    
  • Mathematica
    p = Pochhammer;
    m[3] = 5/2 + Sum[1/((-3)^k*((2+3*k)*p[1/3 -k, k])) + 1/((-3)^k*((1+3*k) *p[2/3 -k, k])) +(-1)^(1-k)/(3^k*(k*p[1-k, -1 +k])), {k, 1, Infinity}]
    (* or *)
    m[3] = (Exp[1/3]/3) (3 + 3^(1/3) (Gamma[1/3] - Gamma[1/3, 1/3]) + 3^(2/3) (Gamma[2/3] - Gamma[2/3, 1/3]));
    RealDigits[m[3], 10, 102][[1]]
  • PARI
    default(realprecision, 100); (exp(1/3)/3)*(3 + 3^(1/3)*(gamma(1/3) - incgam(1/3, 1/3)) + 3^(2/3)*(gamma(2/3) - incgam(2/3, 1/3))) \\ G. C. Greubel, Mar 27 2019
    
  • Sage
    numerical_approx((exp(1/3)/3)*(3 + 3^(1/3)*(gamma(1/3) - gamma_inc(1/3, 1/3)) + 3^(2/3)*(gamma(2/3) - gamma_inc(2/3, 1/3))), digits=100) # G. C. Greubel, Mar 27 2019

Formula

m(k) = (1/k)*exp(1/k)*(k + Sum_{j=1..k-1} k^(j/k)*(gamma(j/k) - gamma(j/k, 1/k))) where gamma(x) is the Euler gamma function and gamma(a,x) the incomplete gamma function.

A288091 Decimal expansion of m(4) = Sum_{n>=0} 1/n!!!!, the 4th reciprocal multifactorial constant.

Original entry on oeis.org

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

Views

Author

Jean-François Alcover, Jun 05 2017

Keywords

Examples

			3.485944977453557745218809044046404795092682320881969407647249998...
		

Crossrefs

Cf. A007662 (n!!!!), A143280 (m(2)), A288055 (m(3)), this sequence (m(4)), A288092 (m(5)), A288093 (m(6)), A288094 (m(7)), A288095 (m(8)), A288096 (m(9)).

Programs

  • Magma
    SetDefaultRealField(RealField(100)); (1/4)*Exp(1/4)*(4 + Sqrt(2)* Gamma(1/4, 1/4) + 2*Gamma(1/2, 1/4) + 2*Sqrt(2)*Gamma(3/4, 1/4)) // G. C. Greubel, Mar 28 2019
    
  • Mathematica
    m[4] = (1/4)*E^(1/4)*(4 + Sqrt[2]*(Gamma[1/4] - Gamma[1/4, 1/4]) + 2*(Sqrt[Pi] - Gamma[1/2, 1/4]) + 2*Sqrt[2]*(Gamma[3/4] - Gamma[3/4, 1/4])); RealDigits[m[4], 10, 104][[1]]
  • PARI
    default(realprecision, 100); (1/4)*exp(1/4)*(4+sqrt(2)*(gamma(1/4) - incgam(1/4, 1/4))+2*(sqrt(Pi) -incgam(1/2, 1/4))+2*sqrt(2)*(gamma(3/4) - incgam(3/4, 1/4))) \\ G. C. Greubel, Mar 28 2019
    
  • Sage
    numerical_approx((1/4)*exp(1/4)*(4 + sqrt(2)*(gamma(1/4) - gamma_inc(1/4, 1/4)) + 2*(sqrt(pi) - gamma_inc(1/2, 1/4)) + 2*sqrt(2)*(gamma(3/4) - gamma_inc(3/4, 1/4))), digits=100) # G. C. Greubel, Mar 28 2019

Formula

m(k) = (1/k)*exp(1/k)*(k + Sum_{j=1..k-1} k^(j/k)*(gamma(j/k) - gamma(j/k, 1/k))) where gamma(x) is the Euler gamma function and gamma(a,x) the incomplete gamma function.

A288092 Decimal expansion of m(5) = Sum_{n>=0} 1/n!5, the 5th reciprocal multifactorial constant.

Original entry on oeis.org

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

Views

Author

Jean-François Alcover, Jun 05 2017

Keywords

Examples

			3.640224467733809734176937236963569060632409516968842599452955763...
		

Crossrefs

Cf. A085157 (n!5), A143280 (m(2)), A288055 (m(3)), A288091 (m(4)), this sequence (m(5)), A288093 (m(6)), A288094 (m(7)), A288095 (m(8)), A288096 (m(9)).

Programs

  • Magma
    SetDefaultRealField(RealField(105)); (1/5)*Exp(1/5)*(5 + (&+[5^(k/5)*Gamma(k/5, 1/5): k in [1..4]])); // G. C. Greubel, Mar 28 2019
    
  • Mathematica
    m[5] = (1/5)*E^(1/5)*(5 + 5^(1/5)*(Gamma[1/5] - Gamma[1/5, 1/5]) + 5^(2/5)*(Gamma[2/5] - Gamma[2/5, 1/5]) + 5^(3/5)*(Gamma[3/5] - Gamma[3/5, 1/5]) + 5^(4/5)*(Gamma[4/5] - Gamma[4/5, 1/5])); RealDigits[m[5], 10, 102][[1]]
  • PARI
    default(realprecision, 105); (1/5)*exp(1/5)*(5 + sum(k=1,4, 5^(k/5)*(gamma(k/5) - incgam(k/5, 1/5)))) \\ G. C. Greubel, Mar 28 2019
    
  • Sage
    numerical_approx((1/5)*exp(1/5)*(5 + sum(5^(k/5)*(gamma(k/5) - gamma_inc(k/5, 1/5)) for k in (1..4))), digits=105) # G. C. Greubel, Mar 28 2019

Formula

m(k) = (1/k)*exp(1/k)*(k + Sum_{j=1..k-1} k^(j/k)*(gamma(j/k) - gamma(j/k, 1/k))) where gamma(x) is the Euler gamma function and gamma(a,x) the incomplete gamma function.

A288094 Decimal expansion of m(7) = Sum_{n>=0} 1/n!7, the 7th reciprocal multifactorial constant.

Original entry on oeis.org

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

Views

Author

Jean-François Alcover, Jun 05 2017

Keywords

Examples

			3.88695965374084349542856991093670567270530958752016048580439533869...
		

Crossrefs

Cf. A114799 (n!7), A143280 (m(2)), A288055 (m(3)), A288091 (m(4)), A288092 (m(5)), A288093 (m(6)), this sequence (m(7)), A288095 (m(8)), A288096 (m(9)).

Programs

  • Magma
    SetDefaultRealField(RealField(105)); (1/7)*Exp(1/7)*(7 + (&+[7^(k/7)*Gamma(k/7, 1/7): k in [1..6]])); // G. C. Greubel, Mar 28 2019
    
  • Mathematica
    m[k_] := (1/k) Exp[1/k] (k + Sum[k^(j/k) (Gamma[j/k] - Gamma[j/k, 1/k]), {j, 1, k - 1}]); RealDigits[m[7], 10, 104][[1]]
    RealDigits[Total[Table[1/Times@@Range[n,1,-7],{n,0,500}]],10,120][[1]] (* Harvey P. Dale, May 21 2023 *)
  • PARI
    default(realprecision, 105); (1/7)*exp(1/7)*(7 + sum(k=1,6, 7^(k/7)*(gamma(k/7) - incgam(k/7, 1/7)))) \\ G. C. Greubel, Mar 28 2019
    
  • Sage
    numerical_approx((1/7)*exp(1/7)*(7 + sum(7^(k/7)*(gamma(k/7) - gamma_inc(k/7, 1/7)) for k in (1..6))), digits=105) # G. C. Greubel, Mar 28 2019

Formula

m(k) = (1/k)*exp(1/k)*(k + Sum_{j=1..k-1} k^(j/k)*(gamma(j/k) - gamma(j/k, 1/k))) where gamma(x) is the Euler gamma function and gamma(a,x) the incomplete gamma function.

A288095 Decimal expansion of m(8) = Sum_{n>=0} 1/n!8, the 8th reciprocal multifactorial constant.

Original entry on oeis.org

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

Views

Author

Jean-François Alcover, Jun 05 2017

Keywords

Examples

			3.9892412126901365441336421348019099438359273924576814826209556653...
		

Crossrefs

Cf. A114800 (n!8), A143280 (m(2)), A288055 (m(3)), A288091 (m(4)), A288092 (m(5)), A288093 (m(6)), A288094 (m(7)), this sequence (m(8)), A288096 (m(9)).

Programs

  • Magma
    SetDefaultRealField(RealField(107)); (1/8)*Exp(1/8)*(8 + (&+[8^(k/8)*Gamma(k/8, 1/8): k in [1..7]])); // G. C. Greubel, Mar 28 2019
    
  • Mathematica
    m[k_] := (1/k) Exp[1/k] (k + Sum[k^(j/k) (Gamma[j/k] - Gamma[j/k, 1/k]), {j, 1, k - 1}]); RealDigits[m[8], 10, 103][[1]]
  • PARI
    default(realprecision, 105); (1/8)*exp(1/8)*(8 + sum(k=1,7, 8^(k/8)*(gamma(k/8) - incgam(k/8, 1/8)))) \\ G. C. Greubel, Mar 28 2019
    
  • Sage
    numerical_approx((1/8)*exp(1/8)*(8 + sum(8^(k/8)*(gamma(k/8) - gamma_inc(k/8, 1/8)) for k in (1..7))), digits=105) # G. C. Greubel, Mar 28 2019

Formula

m(k) = (1/k)*exp(1/k)*(k + Sum_{j=1..k-1} k^(j/k)*(gamma(j/k) - gamma(j/k, 1/k))) where gamma(x) is the Euler gamma function and gamma(a,x) the incomplete gamma function.

A288096 Decimal expansion of m(9) = Sum_{n>=0} 1/n!9, the 9th reciprocal multifactorial constant.

Original entry on oeis.org

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

Views

Author

Jean-François Alcover, Jun 05 2017

Keywords

Examples

			4.08137552016889854407110514660961069462641007731860758843485175...
		

Crossrefs

Cf. A114806 (n!9), A143280 (m(2)), A288055 (m(3)), A288091 (m(4)), A288092 (m(5)), A288093 (m(6)), A288094 (m(7)), A288095 (m(8)), this sequence (m(9)).

Programs

  • Magma
    SetDefaultRealField(RealField(105)); (1/9)*Exp(1/9)*(9 + (&+[9^(k/9)*Gamma(k/9, 1/9): k in [1..8]])); // G. C. Greubel, Mar 28 2019
    
  • Mathematica
    m[k_] := (1/k) Exp[1/k] (k + Sum[k^(j/k) (Gamma[j/k] - Gamma[j/k, 1/k]), {j, 1, k - 1}]); RealDigits[m[9], 10, 102][[1]]
  • PARI
    default(realprecision, 105); (1/9)*exp(1/9)*(9 + sum(k=1,8, 9^(k/9)*(gamma(k/9) - incgam(k/9, 1/9)))) \\ G. C. Greubel, Mar 28 2019
    
  • Sage
    numerical_approx((1/9)*exp(1/9)*(9 + sum(9^(k/9)*(gamma(k/9) - gamma_inc(k/9, 1/9)) for k in (1..8))), digits=105) # G. C. Greubel, Mar 28 2019

Formula

m(k) = (1/k)*exp(1/k)*(k + Sum_{j=1..k-1} k^(j/k)*(gamma(j/k) - gamma(j/k, 1/k))) where gamma(x) is the Euler gamma function and gamma(a,x) the incomplete gamma function.

A342033 Decimal expansion of m(10) = Sum_{n>=0} 1/n!10, the 10th reciprocal multifactorial constant.

Original entry on oeis.org

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

Views

Author

Bhoris Dhanjal, Feb 26 2021

Keywords

Comments

m(k) can be proved to approach a harmonic series (and diverge) as k approaches infinity.

Examples

			4.165243765558384590787262...
For n=10, the series is equal to 1+summation from n=1 to 10 (1/n)=9901/2520.
		

Crossrefs

Cf. A143280 (m(2)), A288055 (m(3)), A288091 (m(4)), A288092 (m(5)), A288093 (m(6)), A288094 (m(7)), A288095 (m(8)), A288096 (m(9)).

Programs

  • Mathematica
    Multifactorial[n_, k_] := Abs[Apply[Times, Range[-n, -1, k]]]
    N[Sum[1/Multifactorial[n, 10], {n, 0, 10000}], 105]
    (* or *)
    ReciprocalFactorialSumConstant[k_] :=
    1/k Exp[1/k] (k + Sum[k^(j/k) Gamma[j/k, 0, 1/k], {j, k - 1}])
    N[ReciprocalFactorialSumConstant[10], 105]

Formula

m(k) = (1/k)*exp(1/k)*(k + Sum_{j=1..k-1} (k^(j/k)*Gamma(j/k, 1/k))) where Gamma(a,x) the incomplete Gamma function.
Showing 1-9 of 9 results.