The developed idea here is to combine properties of Proth numbers k*2n +/- 1, with those of the factorial m!=2.3.4.5.6...m or the primorial m# =2.3.5.7.11...(p<=m) by introducing them in the expression of k :
Choice of n in order to verify the condition of Proth's numbers k<2n :
For FactoProths :
By the utilization of the Stirling's formula for m! it comes approximately
n > (m+1.5)*ln(m)/ln(2) - m*(1+1/ln(2)) + 2
For PrimoProths :
By the utilization of the Tchébycheff 's function Théta(x)=
approximately x, it comes approximately n > m/ln(2) - 1
Generalization :
It is possible to replace the base 2 by an other base b, but the equivalent
Proth test becomes more complex.
and some curiosities (not proths) :
Type | Digits | Who ? | |
6792!*2^4838+1 | 24536 | Zoe Brown-Harvey | |
2613!*21004+1 | 8099 | Didier Boivin | |
239#*2239+1 239#*2239-1 |
Twin |
168
|
|
20#*220+1 20#*220-1 |
Twin |
14
|
|
7#*27+1 7#*27-1 | Twin | 5 | Henri Lifchitz |
37#*231+1 37#*232+1 |
Cunn.L=3 |
23
|
|
41#*29+1 41#*210+1 41#*211+1 41#*212+1 |
Cunn.L=4 | 18 | Henri Lifchitz |
32#*232+1 et 32!*232-1 |
21,46
|
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