A275710 -id:A275710 - cp's OEIS frontend

A001015 Seventh powers: a(n) = n^7.

0, 1, 128, 2187, 16384, 78125, 279936, 823543, 2097152, 4782969, 10000000, 19487171, 35831808, 62748517, 105413504, 170859375, 268435456, 410338673, 612220032, 893871739, 1280000000, 1801088541, 2494357888, 3404825447, 4586471424, 6103515625, 8031810176

Offset: 0

N. J. A. Sloane

For n>0, (a(3*n-1)^7-a(2*n-1)^7-a(n)^7)/(7*(3*n-1)*(2*n-1)*n) = (2*A001106(n)+1)^2 (see Barisien reference, problem 173). - Bruno Berselli, Feb 01 2011

Number of the form a(n) + a(n+1) + ... + a(n+k) is never prime for all n, k>=0. This could be proved by the method indicated in the comment in A256581. - Vladimir Shevelev and Peter J. C. Moses, Apr 04 2015

E.-N. Barisien, Supplemento al Periodico di Matematica, Raffaello Giusti Editore (Livorno), July 1913, p. 135 (Problem 173).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

T. D. Noe, Table of n, a(n) for n = 0..1000
Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992; arXiv:0911.4975 [math.NT], 2009.
Simon Plouffe, 1031 Generating Functions, Appendix to Thesis, Montreal, 1992
Index entries for linear recurrences with constant coefficients, signature (8,-28,56,-70,56,-28,8,-1).

Cf. A000584 (5th powers), A013665 (zeta(7)), A275710 (eta(7)), A300785.

Cf. A003369 - A003379 (sums of 2, ..., 12 positive seventh powers).

A001015:=z*(1191*z^4+120*z^5+1191*z^2+2416*z^3+120*z+z^6+1)/(z-1)^8; # Simon Plouffe in his 1992 dissertation; offset corrected by M. F. Hasler, Feb 01 2011

Table[n^7, {n,0,40}] (* Vladimir Joseph Stephan Orlovsky, Apr 15 2011 *)

makelist(n^7,n,0,20); /* Martin Ettl, Jan 15 2013 */

A001015(n)=n^7 \\ Charles R Greathouse IV, Sep 24 2015

A001015 = lambda n: n**7 # M. F. Hasler, Jul 03 2025

Multiplicative with a(p^e) = p^(7e). - David W. Wilson, Aug 01 2001
Totally multiplicative sequence with a(p) = p^7 for primes p. - Jaroslav Krizek, Nov 01 2009
a(n) = 7*a(n-1) - 21* a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) + 5040. - Ant King, Sep 24 2013
a(n) = n + Sum_{j=0..n-1}{k=1..6}binomial(7,k)*j^(7-k). - Patrick J. McNab, Mar 28 2016
G.f.: x*(1+120*x+1191*x^2+2416*x^3+1191*x^4+120*x^5+x^6)/(1-x)^8. See the Maple program. - Wolfdieter Lang, Oct 14 2016
From Kolosov Petro, Oct 22 2018: (Start)
a(n) = Sum_{k=1..n} A300785(n,k).
a(n) = Sum_{k=0..n-1} A300785(n,k). (End)
From Amiram Eldar, Oct 08 2020: (Start)
Sum_{n>=1} 1/a(n) = zeta(7) (A013665).
Sum_{n>=1} (-1)^(n+1)/a(n) = 63*zeta(7)/64 (A275710). (End)

More terms from James Sellers, Sep 19 2000

A275703 Decimal expansion of the Dirichlet eta function at 6.

Original entry on oeis.org

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

Offset: 0

Terry D. Grant, Aug 05 2016

It appears that each sum of a Dirichlet eta function is 1/2^(x-1) less than the zeta(x), where x is a positive integer > 1. In this case, eta(x) = eta(6) = (31/32)*zeta(6) = 31*(Pi^6)/30240. Therefore eta(6) = 1/2^(6-1) or 1/32nd less than zeta(6) (see A013664). [Edited by Petros Hadjicostas, May 07 2020]

			31*(Pi^6)/30240 = 0.9855510912974...

Cf. A002162 (decimal expansion of value at 1), A072691 (value at 2), A197070 (value at 3), A267315 (value at 4), A267316 (value at 5), A275710 (value at 7).

Cf. A013664, A136677, A334605.

Mathematica
```
RealDigits[31*(Pi^6)/30240,10,100]
```

s = RLF(0); s
RealField(110)(s)
for i in range(1, 10000): s -= (-1)^i / i^6
print(s) # Terry D. Grant, Aug 05 2016

eta(6) = 31*(Pi^6)/30240 = 31*A092732/30240 = Sum_{n>=1} (-1)^(n+1)/n^6.

eta(6) = lim_{n -> infinity} A136677(n)/A334605(n). - Petros Hadjicostas, May 07 2020

A334668 Numerator of Sum_{k=1..n} (-1)^(k+1)/k^7.

Original entry on oeis.org

1, 127, 277877, 35566069, 2778634972433, 2778624972433, 2288319945032390119, 292904812254103669607, 640582959329009845430509, 640582894792751053318381, 12483149055863937257566687990151, 12483148704882733411491577990151, 783299081298153288298872171970695856067

Offset: 1

Petros Hadjicostas, May 07 2020

Lim_{n -> infinity} a(n)/A334669(n) = A275710 = (63/64)*A013665.

			The first few fractions are 1, 127/128, 277877/279936, 35566069/35831808, 2778634972433/2799360000000, 2778624972433/2799360000000, ... = A334668/A334669.

Cf. A013665, A275710, A334669 (denominators).

Numerator @ Accumulate[Table[(-1)^(k + 1)/k^7, {k, 1, 13}]] (* Amiram Eldar, May 08 2020 *)

a(n) = numerator(sum(k=1, n, (-1)^(k+1)/k^7)); \\ Michel Marcus, May 08 2020

A334669 Denominator of Sum_{k=1..n} (-1)^(k+1)/k^7.

Original entry on oeis.org

1, 128, 279936, 35831808, 2799360000000, 2799360000000, 2305393332480000000, 295090346557440000000, 645362587921121280000000, 645362587921121280000000, 12576291107821424895098880000000, 12576291107821424895098880000000, 789143616376081512994335288360960000000

Offset: 1

Petros Hadjicostas, May 07 2020

Lim_{n -> infinity} A334668(n)/a(n) = A275710 = (63/64)*A013665.

			The first few fractions are 1, 127/128, 277877/279936, 35566069/35831808, 2778634972433/2799360000000, 2778624972433/2799360000000, ... = A334668/A334669.

Michael De Vlieger, Table of n, a(n) for n = 1..336

Cf. A013665, A275710, A334668 (numerators).

Denominator @ Accumulate[Table[(-1)^(k + 1)/k^7, {k, 1, 13}]] (* Amiram Eldar, May 08 2020 *)

a(n) = denominator(sum(k=1, n, (-1)^(k+1)/k^7)); \\ Michel Marcus, May 08 2020

A347059 Decimal expansion of the Dirichlet eta function at 9.

Original entry on oeis.org

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

Offset: 0

Sean A. Irvine, Aug 14 2021

			0.998094297541605330767783031852597950...

L. B. W. Jolley, Summation of Series, Dover, 1961, Eq. (306).

Michael I. Shamos, Shamos's catalog of the real numbers (2011).

Cf. A072691, A197070, A267315, A267316, A275703, A275710, A347150, A346927.

First[RealDigits[N[DirichletEta[9],87]]] (* Stefano Spezia, Aug 15 2021 *)

-polylog(9, -1) \\ Michel Marcus, Aug 15 2021

Equals (255/256) * zeta(9).
Equals Sum_{k>=1} (-1)^(k+1) / k^9.
Equals eta(9).

A347150 Decimal expansion of the Dirichlet eta function at 8.

Original entry on oeis.org

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

Offset: 0

Sean A. Irvine, Aug 19 2021

			0.9962330018526478992272892600828036178741251594728980...

L. B. W. Jolley, Summation of Series, Dover, 1961, Eq. (306).

Michael I. Shamos, Shamos's catalog of the real numbers (2011).
Index entries for transcendental numbers

Cf. A072691, A197070, A267315, A267316, A275703, A275710, A346927, A347059.

RealDigits[DirichletEta[8], 10, 100][[1]] (* Amiram Eldar, Aug 20 2021 *)

-polylog(8, -1) \\ Michel Marcus, Aug 20 2021

Equals (127/128) * zeta(8).
Equals 127 * Pi^8 / 1209600.
Equals Sum_{k>=1} (-1)^(k+1) / k^8.
Equals eta(8).

A346927 Decimal expansion of the Dirichlet eta function at 10.

Original entry on oeis.org

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

Offset: 0

Sean A. Irvine, Aug 07 2021

			0.999039507598271565639221845699341831425929649666890...

L. B. W. Jolley, Summation of Series, Dover, 1961, Eq. (306).

Michael I. Shamos, Shamos's catalog of the real numbers (2011).
Index entries for transcendental numbers

Cf. A072691, A197070, A267315, A267316, A275703, A275710, A347150, A347059.

RealDigits[DirichletEta[10], 10, 100][[1]] (* Amiram Eldar, Aug 08 2021 *)

-polylog(10, -1) \\ Michel Marcus, Aug 08 2021

Equals 73 * Pi^10 / (2^9 * 3^5 * 5 * 11).
Equals (511/512) * zeta(10).
Equals Sum_{k>=1} (-1)^(k+1) / k^10.
Equals eta(10).

cp's OEIS Frontend

A001015 Seventh powers: a(n) = n^7.

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A275703 Decimal expansion of the Dirichlet eta function at 6.

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A334668 Numerator of Sum_{k=1..n} (-1)^(k+1)/k^7.

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A334669 Denominator of Sum_{k=1..n} (-1)^(k+1)/k^7.

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A347059 Decimal expansion of the Dirichlet eta function at 9.

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A347150 Decimal expansion of the Dirichlet eta function at 8.

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A346927 Decimal expansion of the Dirichlet eta function at 10.

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