A128938 - OEIS

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A128938

Numbers n such that n(n+1) plus the n-th prime is a prime.

3, 5, 7, 9, 10, 11, 12, 13, 20, 27, 28, 32, 33, 35, 36, 41, 42, 43, 45, 47, 49, 54, 63, 65, 74, 75, 84, 91, 94, 95, 98, 104, 105, 107, 109, 113, 114, 117, 122, 124, 126, 128, 129, 135, 140, 149, 152, 155, 160, 164, 168, 171, 189, 190, 192, 199, 203, 209, 212, 214, 216

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

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

EXAMPLE

Given that 23 is the 9th prime, take 9*10 + 23 = 113, a prime.

MAPLE

a:=proc(n) if isprime(n*(n+1)+ithprime(n))=true then n else fi end: seq(a(n), n=1..270); # Emeric Deutsch, May 05 2007

MATHEMATICA

Select[Range[300], PrimeQ[#(#+1)+Prime[#]]&] (* Harvey P. Dale, Mar 18 2018 *)

PROG