A261809 a(n) = n! - prime(n).

-1, -1, 1, 17, 109, 707, 5023, 40301, 362857, 3628771, 39916769, 479001563, 6227020759, 87178291157, 1307674367953, 20922789887947, 355687428095941, 6402373705727939, 121645100408831933, 2432902008176639929, 51090942171709439927, 1124000727777607679921

Offset: 1

Author

Altug Alkan, Sep 01 2015

Keywords

• sign
• easy

Examples

			For n=4, a(4) = 4! - prime(4) = 24 - 7 = 17.
		

Links

• G. C. Greubel, Table of n, a(n) for n = 1..85

Crossrefs

Cf. A000040, A000142, A121926.

Programs

Magma

[Factorial(n)-NthPrime(n): n in [1..30]]; // Vincenzo Librandi, Sep 02 2015

Mathematica

Table[n! - Prime[n], {n,1,150}] (* G. C. Greubel, Sep 01 2015 *)

PARI

vector(50, n, n!-prime(n))

Formula

a(n) = A000142(n) - A000040(n).