This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
Table[ n!! - 1, {n,0,35} ]
Table[(Prime[n]! + 6)/6, {n, 2, 30}]
Table[(Prime[n]! + 7)/7, {n, 4, 30}]
0 is in the sequence since 0!*2^0 + 1 = 2 is prime.
[n: n in [0..3*10^2] | IsPrime(Factorial(n)*2^n+1)]; // Vincenzo Librandi, Apr 05 2015
Select[Range[0, 20000], PrimeQ[2^#*#! + 1] &]
for(n=0,300,if(ispseudoprime(n!*2^n+1),print1(n,", "))) \\ Derek Orr, Apr 05 2015
from sympy import factorial, isprime
for n in range(0,300):
if isprime(factorial(n)*(2**n)+1):
print(n, end=', ') # Stefano Spezia, Dec 06 2018
a = {}; Do[ k = 1; While[ ! PrimeQ[ (k! + n)/n ], k++ ]; AppendTo[ a, (k! + n)/n ], {n, 1, 100} ]; a [Corrected May 06 2008]
a(n)=my(k,t);until(denominator(t=k++!/n+1)==1&&ispseudoprime(t),);t \\ Charles R Greathouse IV, Jul 19 2011
a = {}; Do[w = FactorInteger[(Prime[n]! + 9)/9]; AppendTo[a, Last[w][[1]]], {n, 4, 16}]; a
Select[Prime[Range[651]],PrimeQ[(2#)!!-1]&]
a = {}; Do[w = FactorInteger[(Prime[n]! + 9)/9]; AppendTo[a, First[w][[1]]], {n, 4, 16}]; a
Table[FactorInteger[p!/9+1][[1,1]],{p,Prime[Range[4,35]]}] (* Harvey P. Dale, Sep 19 2020 *)
a(2) = 3 = 2 + 1 = 2!! + 1 is the 2nd prime of that form. a(4) = 47 = 2*4*6 - 1 = 6!! - 1 is the 4th prime of that form.
r:=91; I:=[1, 1]; lst1:=[n le 2 select I[n] else (n-1)*Self(n-2): n in [1..r]]; lst2:=[]; for c in [1..r] do a:=lst1[c]; for s in [-1..1 by 2] do p:=a+s; if IsPrime(p) and not p in lst2 then Append(~lst2, p); end if; end for; end for; lst2;
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