A091131 -id:A091131 - cp's OEIS frontend

A236289 Decimal expansion of e^2 / (e - 1).

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

Offset: 1

Jaroslav Krizek, Feb 04 2014

			4.3002585353283716597452894764616...

Cf. A001113 (decimal expansion of e), A072334 (decimal expansion of e^2), A091131 (decimal expansion of e-1).

Mathematica
```
RealDigits[E^2/(E-1), 10, 130][[1]]
```

exp(2)/(exp(1)-1) \\ Charles R Greathouse IV, Apr 21 2016

Equals A072334 / A091131.

Mathematica program modified by Harvey P. Dale, Aug 05 2014

A386990 Decimal expansion of Sum_{k>=0} 2/(k!*(k! + 1)).

Original entry on oeis.org

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

Offset: 1

Kelvin Voskuijl, Aug 12 2025

Sum of reciprocals of A055555 (triangular numbers of factorials).

			2.3844273879714288211644804923804481846149857064...

Cf. A000217, A070910 (of n!^2), A055555, A091131 (of n!).

evalf(sum(2/(n!*(n!+1)),n=0..infinity), 120);  # Alois P. Heinz, Aug 13 2025

PARI
```
suminf(k=0, 2/(k!*(k!+1)))
```

sumpos(k=0,1/binomial(k!+1,2)) \\ Charles R Greathouse IV, Aug 19 2025

Equals Sum_{k>=0} 1/A055555(k).

cp's OEIS Frontend

A236289 Decimal expansion of e^2 / (e - 1).

Views

Author

Keywords

Examples

Crossrefs

Programs

Mathematica

PARI

Formula

Extensions

A386990 Decimal expansion of Sum_{k>=0} 2/(k!*(k! + 1)).

Views

Author

Keywords

Comments

Examples

Crossrefs

Programs

Maple

PARI

PARI

Formula