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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A235714 Consider N = numerator( 1/p! + 1/q! ) where p = prime(n), q = prime(n+1) for n = 1,2,3,.... Append N to sequence if it is a prime. 1
2, 7, 43, 157, 7, 72775847, 139, 523, 751, 193, 19183, 22651, 140165120353, 1051, 37057, 433, 7459, 8263, 19248899859613286187907, 1564207235629, 10453, 877, 1993, 45183625504351, 121453, 89248200525047, 1505879629 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..1300

EXAMPLE

43 is in the sequence because ( 1/5! + 1/7! ) = (1/120 + 1/5040) = 43/5040: numerator(43/5040) = 43 which is prime.

MAPLE

KD := proc() local a, b, d, e; a:=ithprime(n)!; b:= ithprime(n+1)!; d:=(1/a) + (1/b); e:=numer(d); if isprime(e) then RETURN (e); fi; end: seq(KD(), n=1..100);

MATHEMATICA

k={}; Do[p=Prime[n]; q=Prime[n+1];  p2=Numerator[1/p!+1/q!]; If[PrimeQ[p2], AppendTo[k, p2]], {n, 150}]; k

CROSSREFS

Cf. A000040, A120833.

Sequence in context: A065298 A091877 A050631 * A146759 A303031 A220220

Adjacent sequences:  A235711 A235712 A235713 * A235715 A235716 A235717

KEYWORD

nonn

AUTHOR

K. D. Bajpai, Jan 15 2014

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 11 10:29 EDT 2021. Contains 343788 sequences. (Running on oeis4.)