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Almost integers

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Almost integers (or near integers[1][2]) are numbers which, although not being integers on account of having a fractional part, are very close to integers and can be mistaken for such as the result of a loss of machine precision during a calculation. For example, 99.99999999999 is an almost integer that is almost the integer 100.

Ramanujan's constant

Ramanujan's constant is amazingly close to an integer, the first 12 digits after the decimal point being 9. The decimal expansion of Ramanujan's constant is

A060295 Decimal expansion of e^(Pi*sqrt(163)).

{2, 6, 2, 5, 3, 7, 4, 1, 2, 6, 4, 0, 7, 6, 8, 7, 4, 3, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 2, 5, 0, 0, 7, 2, 5, 9, 7, 1, 9, 8, 1, 8, 5, 6, 8, 8, 8, 7, 9, 3, 5, 3, 8, 5, 6, 3, 3, 7, 3, 3, 6, 9, 9, 0, 8, 6, 2, 7, 0, 7, 5, 3, 7, 4, 1, 0, ...}

Pi^3

Pi^3 is somewhat close to an integer, the first 2 digits after the decimal point being 0. The decimal expansion of is

A091925 Decimal expansion of pi^3.

{3, 1, 0, 0, 6, 2, 7, 6, 6, 8, 0, 2, 9, 9, 8, 2, 0, 1, 7, 5, 4, 7, 6, 3, 1, 5, 0, 6, 7, 1, 0, 1, 3, 9, 5, 2, 0, 2, 2, 2, 5, 2, 8, 8, 5, 6, 5, 8, 8, 5, 1, 0, 7, 6, 9, 4, 1, 4, 4, 5, 3, 8, 1, 0, 3, 8, 0, 6, 3, 9, 4, 9, 1, 7, 4, 6, 5, 7, ...}

Also, observe that the decimal expansion of is nearly

Notes

  1. One might have wanted to distinguish between the two cases of near integers: slightly less than an integer (almost integers) and slightly more than an integer (quasi integers), but according to common usage, almost integers means near integers. Also, quasi-integers (hyphenated) (Ahlswede and Khachatrian 1996) refers to a different concept.
  2. Rudolf Ahlswede and Levon H. Khachatrian (Bielefeld), Sets of integers and quasi-integers with pairwise common divisor, ACTA ARITHMETICA, LXXIV.2 (1996).