The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A264867 Numbers n such that n!3 + 3^8 is prime, where n!3 = n!!! is a triple factorial number (A007661). 1
 2, 5, 10, 26, 34, 35, 37, 59, 68, 76, 104, 106, 188, 193, 242, 278, 287, 290, 572, 772, 773, 1304, 2384, 2716, 3715, 4562, 6706, 11489, 11711, 21602, 24295, 24775, 27224, 29935, 37856 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Corresponding primes are 6563, 6571, 6841, 2504908961, 17961239302561, 81359229958561, 664565853958561, ... Terms > 68 correspond to probable primes. a(36) > 50000. LINKS Henri & Renaud Lifchitz, PRP Records. Search for n!3+3^8 Joe McLean, Interesting Sources of Probable Primes OpenPFGW Project, Primality Tester EXAMPLE 10!3 + 3^4 = 10*7*4*1 + 6561 = 6841 is prime, so 10 is in the sequence. MATHEMATICA MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]]; Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 3] + 3^8] &] PROG (PARI) is(n)=ispseudoprime(n!!! + 3^8) \\ Anders HellstrÃ¶m, Nov 27 2015 (PARI) tf(n) = prod(i=0, (n-1)\3, n-3*i); for(n=1, 1e4, if(ispseudoprime(tf(n) + 3^8), print1(n , ", "))) \\  Altug Alkan, Dec 03 2015 CROSSREFS Cf. A007661, A037082, A084438, A243078. Sequence in context: A297860 A002094 A212709 * A115725 A305577 A196630 Adjacent sequences:  A264864 A264865 A264866 * A264868 A264869 A264870 KEYWORD nonn,more AUTHOR Robert Price, Nov 26 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 3 05:29 EDT 2020. Contains 334798 sequences. (Running on oeis4.)