A128662 - OEIS

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A128662

Numbers k such that p(k+1)# + p(k)# - p(k-1)# + 1 is prime where p(i)#=product of first i primes=A002110(i).

8, 13, 14, 15, 30, 41, 71, 85, 97, 132, 231, 282, 424, 509, 1346, 1348, 3684

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..17.

MATHEMATICA

Flatten[Position[Partition[FoldList[Times, Prime[Range[1350]]], 3, 1], _?(PrimeQ[ #[[2]]+#[[3]]-#[[1]]+1]&), 1, Heads->False]]+1 (* Harvey P. Dale, May 30 2018 *)

PROG

(PARI) P(n) = factorback(primes(n)); \\ A002110

isoko(k) = ispseudoprime(P(k+1)+P(k)-P(k-1)+1); \\ Michel Marcus, Sep 11 2022

CROSSREFS

Cf. A002110, A128420, A128421, A128657, A128658, A128659, A128660, A128661.

Sequence in context: A070476 A335167 A124159 * A133192 A063684 A059194

Adjacent sequences: A128659 A128660 A128661 * A128663 A128664 A128665

KEYWORD

nonn,more

AUTHOR

Pierre CAMI, Mar 19 2007

EXTENSIONS

a(17) from Michael S. Branicky, Jun 23 2023

STATUS

approved