A276595
Denominator of the rational part of the sum of reciprocals of even powers of even numbers, i.e., Sum_{k>=1} 1/(2*k)^(2*n).
Original entry on oeis.org
24, 1440, 60480, 2419200, 95800320, 2615348736000, 149448499200, 21341245685760000, 10218188434341888000, 1605715325396582400000, 28202200078783610880000, 3387648273463487338905600000, 372269041039943663616000000, 75786531374911731038945280000000
Offset: 1
-
seq(denom(sum(1/(2*k)^(2*n),k=1..infinity)/Pi^(2*n)),n=1..24);
seq(denom(bernoulli(2*n)/2/(2*n)!),n=1..24); # Robert Israel, Sep 18 2016
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Table[Denominator[Zeta[2*n]/(2*Pi)^(2*n)], {n, 1, 30}] (* Terry D. Grant, Jun 19 2018 *)
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a(n) = denominator(bernfrac(2*n)/(2*(2*n)!)); \\ Michel Marcus, Jul 05 2018
A100594
Floor of Pi^(2*n)/Zeta(2*n).
Original entry on oeis.org
6, 90, 945, 9450, 93555, 924041, 9121612, 90030844, 888579011, 8769948429, 86555983552, 854273468992, 8431341566236, 83214006759229, 821289329637860, 8105800788023426, 80001047145799660, 789578687036411293
Offset: 1
Joseph Biberstine (jrbibers(AT)indiana.edu), Nov 30 2004
a(1)=6 because Zeta(2*1)=Pi^2/6 implies Pi^2/Zeta(2)=6 and floor(6)=6.
a(6)=924041 because Zeta(2*6)=691/638512875*Pi^12 implies Pi^12/Zeta(12)=638512875/691 and floor(638512875/691)=924041.
-
seq(simplify(floor(Pi^(2*k)/Zeta(2*k))),k=1..24);
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Table[Floor[Pi^(2*n)/Zeta[2*n]],{n,20}] (* Terry D. Grant, May 28 2017 *)
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{a(n)=if(n<1, 0, floor(-2*(2*n)!/(-4)^n/bernfrac(2*n)))} /* Michael Somos, Feb 18 2007 */
A104007
Denominators of coefficients in expansion of x^2*(1-exp(-2*x))^(-2).
Original entry on oeis.org
4, 2, 12, 6, 60, 90, 378, 945, 2700, 9450, 20790, 93555, 116093250, 638512875, 1403325, 18243225, 43418875500, 325641566250, 4585799468250, 38979295480125, 161192575293750, 1531329465290625, 640374140030625, 13447856940643125, 17558223649022306250
Offset: 0
See
A098087 for further information.
-
Denominator[ CoefficientList[ Series[x^2*(1 - E^(-2x))^(-2), {x, 0, 33}], x]] (* Robert G. Wilson v, Apr 20 2005 *)
Denominator[
Function[{n},
Piecewise[{{1/2 (-1 + n) Zeta[n], Mod[n, 2] == 0}, {Zeta[-1 + n],
Mod[n, 2] == 1}}]] /@ Range[0, 20]] (* Andrey Mitin, Aug 16 2020 *)
A276594
Numerator of the rational part of the sum of reciprocals of even powers of even numbers, i.e., Sum_{k>=1} 1/(2*k)^(2*n).
Original entry on oeis.org
1, 1, 1, 1, 1, 691, 1, 3617, 43867, 174611, 77683, 236364091, 657931, 3392780147, 1723168255201, 7709321041217, 151628697551, 26315271553053477373, 154210205991661, 261082718496449122051, 1520097643918070802691, 2530297234481911294093
Offset: 1
A295231
Numerators of (-1)^(n+1) * (2*n)! * (2^(2*n)+1)/(B_{2*n} * 2^(4*n-1)), where B_{n} is the Bernoulli number.
Original entry on oeis.org
-4, 15, 765, 61425, 1214325, 95893875, 2615987248875, 298915241625, 10670785663663125, 10218227413637368125, 1605716856726047690625, 56404413605424162403125, 3387648475383059302662121875, 744538093174369303262578125
Offset: 0
Zeta(2) = Pi^2/6 > 1 + 1/2^2, so Pi^2 > 15/2.
Zeta(4) = Pi^4/90 > 1 + 1/2^4, so Pi^4 > 765/8.
Zeta(6) = Pi^6/945 > 1 + 1/2^6, so Pi^6 > 61425/64.
A295232
Denominator of (-1)^(n+1) * (2*n)! * (2^(2*n)+1)/(B_{2*n} * 2^(4*n-1)), where B_{n} is the Bernoulli number.
Original entry on oeis.org
1, 2, 8, 64, 128, 1024, 2830336, 32768, 118521856, 11499470848, 183092903936, 651652235264, 3965531409350656, 88306004000768, 1821484971735384064, 7400951301593676906496, 16555640873195841519616, 2604961188466481168384
Offset: 0
Zeta(2) = Pi^2/6 > 1 + 1/2^2, so Pi^2 > 15/2.
Zeta(4) = Pi^4/90 > 1 + 1/2^4, so Pi^4 > 765/8.
Zeta(6) = Pi^6/945 > 1 + 1/2^6, so Pi^6 > 61425/64.
A370411
Square array T(n, k) = denominator( zeta_r(2*n) * sqrt(A003658(k + 2)) / Pi^(4*n) ), read by antidiagonals, where zeta_r is the Dedekind zeta-function over r and r is the real quadratic field with discriminant A003658(k + 2).
Original entry on oeis.org
1, 75, 1, 16875, 24, 1, 221484375, 34560, 18, 1, 116279296875, 116121600, 58320, 39, 1, 12950606689453125, 780337152000, 440899200, 296595, 51, 1, 4861333986053466796875, 8899589151129600, 6666395904000, 68420017575, 663255, 63, 1, 677114376628875732421875
Offset: 0
The array begins:
1, 1, 1, 1, 1
75, 24, 18, 39, 51
16875, 34560, 58320, 296595, 663255
221484375, 116121600, 440899200, 68420017575, 20126472975
116279296875, 780337152000, 6666395904000, 93393323989875, 10382542981248375
Cf.
A002432 (denominators zeta(2*n)/Pi^(2*n)).
Cf.
A046988 (numerators zeta(2*n)/Pi^(2*n)).
Coefficients of Dedekind zeta functions for real quadratic number fields of discriminants 5, 8, 12, 13, 17, 21, 24, 28, 29, 33, 37, 40 are
A035187,
A035185,
A035194,
A035195,
A035199,
A035203,
A035188,
A035210,
A035211,
A035215,
A035219,
A035192, respectively.
-
\p 700
row(n) = {v=[]; for(k=2, 30, if(isfundamental(k), v=concat(v, denominator(bestappr(sqrt(k)*lfun(x^2-(k%2)*x-floor(k/4), 2*n)/Pi^(4*n)))))); v}
z(n,d) = if(n == 0, 0,(1/(-2*n))*bernfrac(2*n)*d^(2*n-1)*sum(k=1,d-1, kronecker(d, k)*subst(bernpol(2*n),x,k/d)*(1/(-2*n))))
row(n) = {v=[]; for(k=2, 100, if(isfundamental(k), v=concat(v, denominator((2^(n*4)*n^2*z(n,k))/((2*n)!^2 * (k^(2*n-1))))))); v} \\ more accuracy here
-
# Only suitable for small n and k
def T(n, k):
discs = [fundamental_discriminant(i) for i in range(1, 4*k+10)]
D = sorted(list(set(discs)))[k+1]
zetaK = QuadraticField(D).zeta_function(1000)
val = (zetaK(2*n)*sqrt(D)/(pi^(4*n))).n(1000).nearby_rational(2^-900)
return val.denominator() # Robin Visser, Mar 19 2024
A370412
Square array T(n, k) = numerator( zeta_r(2*n) * sqrt(A003658(k + 2)) / Pi^(4*n) ), read by antidiagonals, where zeta_r is the Dedekind zeta-function over r and r is the real quadratic field with discriminant A003658(k + 2).
Original entry on oeis.org
0, 2, 0, 4, 1, 0, 536, 11, 1, 0, 2888, 361, 23, 2, 0, 3302008, 24611, 1681, 116, 4, 0, 12724582576, 2873041, 257543, 267704, 328, 4, 0, 18194938976, 27233033477, 67637281, 3741352, 92656, 88, 1, 0, 875222833138832, 11779156811, 18752521534133, 1156377368, 479214352, 287536, 29, 2, 0
Offset: 0
The array begins:
0, 0, 0, 0, 0
2, 1, 1, 2, 4
4, 11, 23, 116, 328
536, 361, 1681, 267704, 92656
2888, 24611, 257543, 3741352, 479214352
3302008, 2873041, 67637281, 1156377368, 14816172016
12724582576, 27233033477, 18752521534133, 753075777246704, 16476431095568992
Cf.
A002432 (denominators zeta(2*n)/Pi^(2*n)).
Cf.
A046988 (numerators zeta(2*n)/Pi^(2*n)).
Coefficients of Dedekind zeta functions for real quadratic number fields of discriminants 5, 8, 12, 13, 17, 21, 24, 28, 29, 33, 37, 40 are
A035187,
A035185,
A035194,
A035195,
A035199,
A035203,
A035188,
A035210,
A035211,
A035215,
A035219,
A035192, respectively.
-
\p 700
row(n) = {v=[]; for(k=2, 50, if(isfundamental(k), v=concat(v, numerator(bestappr(sqrt(k)*lfun(x^2-(k%2)*x-floor(k/4), 2*n)/Pi^(4*n)))))); v}
z(n,d) = if(n == 0, 0,(1/(-2*n))*bernfrac(2*n)*d^(2*n-1)*sum(k=1,d-1, kronecker(d, k)*subst(bernpol(2*n),x,k/d)*(1/(-2*n))))
row(n) = {v=[]; for(k=2, 100, if(isfundamental(k), v=concat(v, numerator((2^(n*4)*n^2*z(n,k))/((2*n)!^2 * (k^(2*n-1))))))); v} \\ more accuracy here
-
# Only suitable for small n and k
def T(n, k):
discs = [fundamental_discriminant(i) for i in range(1, 4*k+10)]
D = sorted(list(set(discs)))[k+1]
zetaK = QuadraticField(D).zeta_function(1000)
val = (zetaK(2*n)*sqrt(D)/(pi^(4*n))).n(1000).nearby_rational(2^-900)
return val.numerator() # Robin Visser, Mar 19 2024
A340471
Denominators of an approximation to zeta(n)/Pi^n.
Original entry on oeis.org
2, 6, 28, 90, 1488, 945, 182880, 9450, 8241408, 93555, 14856307200, 638512875, 1569400842240, 18243225, 5713142135500800, 325641566250, 1096948397364019200, 38979295480125, 6713362606110031872000, 1531329465290625, 408173030347971900211200, 13447856940643125
Offset: 1
1/2, 1/6, 1/28, 1/90, 5/1488, 1/945, 61/182880, 1/9450, 277/8241408, 1/93555, 50521/14856307200, 691/638512875, ...
Values are approximate for odd indices, exact for even indices:
zeta(1) ~ 1/2 zeta(2) = Pi^2/6
zeta(3) ~ Pi^3/28 zeta(4) = Pi^4/90
zeta(5) ~ 5*Pi^5/1488 zeta(6) = Pi^6/945
zeta(7) ~ 61*Pi^7/182880, zeta(8) = Pi^8/9450
...
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a[k_] := Denominator[(1/(4 (1 - 2^-k) k!)
D[\[Lambda] Tan[(\[Pi] + \[Lambda])/4], {\[Lambda],
k}]) /. {\[Lambda] -> 0}]
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a(n) = {my(t=tan(x/4 + O(x*x^n))); denominator(polcoef(x*(1 + t)/(1 - t), n)/((4-2^(2-n))))} \\ Andrew Howroyd, Jan 10 2021
A351806
Denominator of zeta({6}_n)/Pi^(6*n).
Original entry on oeis.org
1, 945, 212837625, 64965492466875, 432684797065192546875, 1347828286825972065254765625, 197885500589205605585596463448046875, 18132629348577543860598956218936672646484375, 3673787208165374996876652878250276546299488037109375
Offset: 0
- J. M. Borwein, D. M. Bradley, and D. J. Broadhurst, Evaluations of k-fold Euler/Zagier sums: a compendium of results for arbitrary k, arXiv:hep-th/9611004, 1996.
- Roudy El Haddad, Multiple Sums and Partition Identities, arXiv:2102.00821 [math.CO], 2021.
- Roudy El Haddad, A generalization of multiple zeta value. Part 2: Multiple sums. Notes on Number Theory and Discrete Mathematics, 28(2), 2022, 200-233, DOI: 10.7546/nntdm.2022.28.2.200-233.
Cf.
A002432 (denominators of zeta(2*n)/Pi^(2*n)).
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a[n_] := Denominator[6*2^(6*n)/(6*n + 3)!]; Array[a, 9, 0] (* Amiram Eldar, Feb 19 2022 *)
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a(n) = denominator(6*2^(6*n)/(6*n + 3)!); \\ Michel Marcus, Feb 22 2022
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