A143932 a(n) = smallest positive prime number of the form x^2 - n! (where x is a positive integer).

3, 2, 3, 97, 241, 241, 1201, 3361, 5569, 61441, 240769, 915049, 240769, 17302321, 7076521, 49186201, 2100735289, 1074527281, 23971813321, 32354445841, 68820869329, 2992426816129, 26238323995129, 104071698229321

Offset

1,1

Comments

For smallest positive integers x see A143931. Prime x see A143933.

Links

Table of n, a(n) for n=1..24.

Example

a(1)=3 because 2^2 - 1! = 3;
a(2)=2 because 2^2 - 2! = 2;
a(3)=3 because 3^2 - 3! = 3;
a(4)=97 because 11^2 - 4! = 97.

Mathematica

b = {}; Do[k = Round[Sqrt[n! ]] + 1; While[ ! PrimeQ[k^2 - n! ], k++ ]; AppendTo[b, k^2-n! ], {n, 1, 50}]; b

Crossrefs

Cf. A121926, A143931, A143933.

Sequence in context: A139075 A089750 A109591 * A304496 A195258 A370450

Adjacent sequences: A143929 A143930 A143931 * A143933 A143934 A143935

Keyword

nonn

Author

Artur Jasinski, Sep 05 2008

Status

approved