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A105454 Numbers n such that n*prime(n)+(n+1)*prime(n+1) is prime. 4
3, 4, 6, 7, 8, 10, 12, 14, 15, 18, 19, 20, 21, 24, 25, 26, 29, 32, 34, 35, 49, 50, 54, 57, 59, 60, 62, 72, 77, 79, 87, 89, 94, 101, 104, 111, 115, 132, 134, 137, 138, 140, 141, 142, 148, 154, 161, 162, 164, 167, 168, 180, 181, 182, 183, 186, 190, 192, 195, 203, 204 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Or, numbers n such that A152117(n) is prime. - Zak Seidov, Feb 05 2016

LINKS

Table of n, a(n) for n=1..61.

EXAMPLE

4*prime(4)+5*prime(5) = 4*7+5*11 = 83 prime.

MATHEMATICA

bb={}; Do[If[PrimeQ[n Prime[n]+(n+1)Prime[n+1]], bb=Append[bb, n]], {n, 400}]; bb

Select[Range[250], PrimeQ[# Prime[#]+(#+1)Prime[#+1]]&] (* Harvey P. Dale, Dec 08 2011 *)

PROG

(PARI) isok(n) = isprime(n*prime(n)+(n+1)*prime(n+1)); \\ Michel Marcus, Feb 05 2016

(PARI) lista(nn) = {for(n=1, nn, if(ispseudoprime(n*prime(n)+(n+1)*prime(n+1)), print1(n, ", "))); } \\ Altug Alkan, Feb 05 2016

(MAGMA) [n: n in [1..250] | IsPrime(n*NthPrime(n)+(n+1)*NthPrime(n+1))]; // Vincenzo Librandi, Feb 06 2016

CROSSREFS

Cf. A152117, A119487.

Sequence in context: A274829 A087758 A227019 * A283482 A283471 A127260

Adjacent sequences:  A105451 A105452 A105453 * A105455 A105456 A105457

KEYWORD

nonn

AUTHOR

Zak Seidov, May 02 2005

STATUS

approved

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Last modified January 28 12:58 EST 2020. Contains 331321 sequences. (Running on oeis4.)