A113933 (F5,F7,F8,F9,F10,F11,F12,F14) - 10^n = prime where F stands for the Fermat numbers 2^2^x + 1 where x corresponds to 5,7,8,9,10,11,12 and 14.

2, 16, 28, 6, 30, 72, 130, 255

Offset

2,1

Comments

This sequence shows that the difference between a composite number and a prime rests on the modification of a single decimal digit. Note that F6 and F13 regarding the Fermat numbers are exceptions to this rule.

Links

Table of n, a(n) for n=2..9.

Example

F5 - 10^2 = 4294967197 = prime

Mathematica

Position[PrimeQ[Table[2^2^5 + 1 - 10^n, {n, 10}]], True]

Crossrefs

Sequence in context: A067566 A067555 A108705 * A127871 A242933 A321308

Adjacent sequences: A113930 A113931 A113932 * A113934 A113935 A113936

Keyword

nonn

Author

Joao Carlos Leandro da Silva (zxawyh66(AT)yahoo.com), Jan 30 2006

Status

approved