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A091417 Integers n which are not the difference of 2 integers A and B where A is less than or equal to n such that AB+1 and AB-1 are both primes. In other words, the product A*B cannot be the middle integer of a twin prime pair. 1
8, 9, 10, 15, 18, 20, 30, 40, 51, 58, 60, 65, 75, 96, 100, 110, 120, 170, 195, 240, 250, 260, 315, 330, 345, 390, 540, 630, 750, 780, 910, 1020, 1720, 1890 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Sequence may be finite. Next term after 1890 if it exists must be greater than 867750.

LINKS

Table of n, a(n) for n=1..34.

EXAMPLE

8 is a member: 8 is the difference between these pairs of integers: (9-1) (10-2) (11-3) (12-4) (13-5) (14-6) (15-7) (16-8). Their products (9*1) (10*2), etc. plus and minus 1 are not primes and therefore the products cannot be the middle integers of twin prime sets.

CROSSREFS

Cf. A090695, A091182, A091183. A091418.

Sequence in context: A271211 A072381 A046415 * A069237 A334728 A070480

Adjacent sequences:  A091414 A091415 A091416 * A091418 A091419 A091420

KEYWORD

nonn,fini

AUTHOR

William F. Sindelar (w_sindelar(AT)juno.com), Jan 05 2004

STATUS

approved

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Last modified June 6 01:16 EDT 2020. Contains 334858 sequences. (Running on oeis4.)