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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A303670 Decimal expansion of Product_{k>=1} Gamma(1 + 1/k^2).

Original entry on oeis.org

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

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Author

Vaclav Kotesovec, Apr 28 2018

Keywords

Examples

			0.73302494338583016910945992884780993498453383505001022198223...
		

Crossrefs

Programs

  • Maple
    Digits := 120: evalf(product(GAMMA(1+1/n^2), n = 1..infinity));
    evalf(exp(-gamma*Pi^2/6 + Sum((-1)^k*Zeta(k)*Zeta(2*k)/k, k=2..infinity)), 121); # Vaclav Kotesovec, Mar 09 2019
  • Mathematica
    RealDigits[NProduct[Gamma[1 + 1/n^2], {n, 1, Infinity}, WorkingPrecision -> 120, NProductFactors -> 1000], 10, 70][[1]]
  • PARI
    exp(-Euler*Pi^2/6 + sumalt(k=2, (-1)^k*zeta(k)*zeta(2*k)/k)) \\ Vaclav Kotesovec, Mar 09 2019

Formula

Equals Product_{k>=1} Gamma(1/k^2) / k^2.
Equals exp(-gamma*Pi^2/6 + Sum_{k>=2} (-1)^k*zeta(k)*zeta(2*k)/k), where gamma is the Euler-Mascheroni constant A001620. - Vaclav Kotesovec, Mar 09 2019
Equals exp(-gamma*Pi^2/6 + A306774).

A324589 a(n) = Product_{j=1..n, k=1..n} (1 + (j*k)^2).

Original entry on oeis.org

1, 2, 850, 9541930000, 62954953875193006250000, 2232026314050243695025069057306526600000000, 2378738322196706013428557679949358718247570924314917636028125000000000
Offset: 0

Views

Author

Vaclav Kotesovec, Mar 09 2019

Keywords

Comments

Product_{j>=1, k>=1} (1 + 1/(j^3*k^3)) = 3.07044599622955113359633939413741321690850038945774000273914990604256664558...

Crossrefs

Programs

  • Maple
    a:= n-> mul(mul((i*j)^2+1, i=1..n), j=1..n):
    seq(a(n), n=0..7);  # Alois P. Heinz, Jun 24 2023
  • Mathematica
    Table[Product[j^2*k^2 + 1, {j, 1, n}, {k, 1, n}], {n, 1, 8}]
    Round[Table[Product[k^(1 + 2*n) * Gamma[1 - I/k + n] * Gamma[1 + I/k + n] * Sinh[Pi/k]/Pi, {k, 1, n}], {n, 1, 8}]]

Formula

a(n) ~ c * 4^n * Pi^(2*n) * n^(2*n*(2*n+1)) / exp(4*n^2), where c = 14.2467190172413789737182639605567415110439648274273645215657580983939589... = exp(1/3) * Product_{j>=1, k>=1} (1 + 1/(j^2*k^2)). - Vaclav Kotesovec, Mar 28 2019

Extensions

a(0)=1 prepended by Alois P. Heinz, Jun 24 2023
Showing 1-2 of 2 results.