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!)
A088708 Numbers n which are a product of two primes j and k such that n+j-k and n-j+k are both primes. 5
6, 10, 15, 22, 57, 85, 87, 142, 187, 217, 235, 267, 274, 295, 339, 382, 505, 565, 579, 589, 667, 694, 799, 835, 849, 862, 889, 922, 1059, 1111, 1159, 1317, 1339, 1555, 1569, 1797, 1969, 1977, 2122, 2182, 2217, 2227, 2229, 2245, 2319, 2335, 2359, 2497, 2577 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

In other words, numbers n which are a product of two distinct primes a and b such that n+-d are primes, where d is the difference between a and b.

LINKS

Table of n, a(n) for n=1..49.

EXAMPLE

a(10)=217 because 217 has only one pair of prime factors (7 and 31) and both 217+7-31 and 217-7+31 (193 and 241) are primes.

MATHEMATICA

pdpQ[{a_, b_}]:=Module[{d=b-a}, AllTrue[a*b+{d, -d}, PrimeQ]]; With[{upto = 2600}, Select[ Times@@@Select[Subsets[Prime[Range[upto/2]], {2}], pdpQ]// Union, #<=upto&]] (* Harvey P. Dale, Aug 02 2016 *)

CROSSREFS

Cf. A001358.

Sequence in context: A157344 A332765 A093773 * A174872 A229273 A315285

Adjacent sequences:  A088705 A088706 A088707 * A088709 A088710 A088711

KEYWORD

nonn

AUTHOR

Chuck Seggelin (barkeep(AT)plastereddragon.com), Oct 11 2003

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 July 24 06:56 EDT 2021. Contains 346273 sequences. (Running on oeis4.)