A113933 - OEIS

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

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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