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A173915 Primes of the form R(n!!+1) 3
2, 3, 61, 601, 1483, 631531, 12912301, 67501394731, 622341432613, 10006712616835423333725869390401 (list; graph; refs; listen; history; text; internal format)
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

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Last modified June 25 06:20 EDT 2021. Contains 345452 sequences. (Running on oeis4.)