A073743 -id:A073743 - cp's OEIS frontend

A379356 Decimal expansion of log(cosh(1)).

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

Offset: 0

Artur Jasinski, Dec 21 2024

			0.4337808304830271870264946849...

Cf. A073743.

Mathematica
```
RealDigits[Log[Cosh[1]], 10, 105][[1]]
```

log(cosh(1)) \\ Stefano Spezia, Dec 22 2024

Equals log(A073743).
Equals Integral_{x=0..1} (1 - x)/cosh(x)^2 dx.
Equals Integral_{x=0..1} tanh(x) dx. - Amiram Eldar, Dec 21 2024

A385405 Decimal expansion of 1/(2*cosh(1)^2).

Original entry on oeis.org

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

Offset: 0

Amiram Eldar, Jul 25 2025

			0.20998717080701303469724836952085072245859336411538...

Hideyuki Ohtsuka, Problem 11978, Problems and Solutions, The American Mathematical Monthly, Vol. 124, No. 5 (2017), p. 465; A Sum of Hyperbolic Cosines of Fibonacci Numbers, Solution to Problem 11978 by Kyle Gatesman, ibid., Vol. 126, No. 2 (2019), p. 185.

Cf. A000045, A073743.

RealDigits[1/(2*Cosh[1]^2), 10, 120][[1]]

PARI
```
1/(2*cosh(1)^2)
```

Equals 1/(2*A073743^2).

Equals Sum_{n>=0} (-1)^n/(cosh(Fibonacci(n)) * cosh(Fibonacci(n+3))) (Ohtsuka, 2017).

cp's OEIS Frontend

A379356 Decimal expansion of log(cosh(1)).

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