This site is supported by donations to The OEIS Foundation.

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A247097 a(n) = least integer m such that prime(n)+m and prime(n+1)+m are prime. 2
 2, 6, 6, 6, 6, 12, 18, 8, 12, 6, 6, 18, 24, 6, 8, 12, 6, 12, 30, 10, 18, 14, 12, 6, 6, 6, 30, 18, 24, 36, 20, 12, 18, 30, 6, 10, 30, 6, 18, 12, 42, 6, 30, 30, 12, 16, 6, 12, 48, 18, 30, 30, 6, 6, 8, 12, 6, 30, 30, 24, 24, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS In most cases terms are congruent to 0 mod 6. Out of the first 1000 terms, 830 are multiples of 6. It is conjectured that a(n) always exists. LINKS Colin Barker, Table of n, a(n) for n = 2..10000 EXAMPLE Offset is 2, hence first term corresponds to n=2. For n=2, prime(n)=3,  prime(n+1)=5, m=2, and 3+2 and 5+2 are prime. For n=3, m=6, 5+6 and 7+6 are prime. MATHEMATICA lm[{a_, b_}]:=Module[{m=2}, While[!PrimeQ[a+m]||!PrimeQ[b+m], m+=2]; m]; lm/@ Partition[ Prime[Range[2, 70]], 2, 1] (* Harvey P. Dale, Oct 02 2018 *) PROG (PARI) s=[]; for(n=2, 100, p=prime(n); q=prime(n+1); m=1; while(!(isprime(p+m)&&isprime(q+m)), m++); s=concat(s, m)); s \\ Colin Barker, Nov 18 2014 CROSSREFS Sequence in context: A184409 A137479 A304363 * A258576 A278253 A294961 Adjacent sequences:  A247094 A247095 A247096 * A247098 A247099 A247100 KEYWORD nonn AUTHOR Zak Seidov, Nov 18 2014 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.

Last modified January 20 17:05 EST 2019. Contains 319335 sequences. (Running on oeis4.)