A173915 Primes of the form R(n!!+1)

2, 3, 61, 601, 1483, 631531, 12912301, 67501394731, 622341432613, 10006712616835423333725869390401

Offset

1,1

Links

Paolo P. Lava & Giorgio Balzarotti, Table of n, a(n) for n = 1..11

Example

n=7 -> 7!!+1 = 105+1=106 -> R(106)=601 is prime

Maple

P:=proc(i) local a, b, k, n, v; v:=array(1..10000); for n from 1 by 1 to i do a:=1; k:=doublefactorial(n)+1; while k>0 do v[a]:=k-(trunc(k/10)*10); k:=trunc(k/10); a:=a+1; od; k:=0; for b from a-1 by -1 to 1 do k:=k+v[b]*10^(a-1-b); od; if isprime(k) then print(k); fi; od; end: P(2000);

Crossrefs

Cf. A173913, A173914, A173916.

Sequence in context: A062308 A072875 A093551 * A293041 A284755 A061452

Adjacent sequences: A173912 A173913 A173914 * A173916 A173917 A173918

Keyword

nonn

Author

Paolo P. Lava and Giorgio Balzarotti, Mar 02 2010

Status

approved