A160666 Numbers whose distance to the closest prime number is a prime number.
0, 9, 15, 21, 25, 26, 27, 33, 34, 35, 39, 45, 49, 50, 51, 55, 56, 57, 63, 64, 65, 69, 75, 76, 77, 81, 85, 86, 87, 91, 92, 94, 95, 99, 105, 111, 115, 116, 118, 120, 122, 124, 125, 129, 133, 134, 135, 141, 142, 144, 146, 147, 153, 154, 155, 159, 160, 161, 165, 169, 170
Offset: 1
Keywords
Links
- K. Stern, Table of n, a(n) for n=1..10000
Programs
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Maple
isA160666 := proc(n) local ppl,pmi ; if isprime(n) then RETURN(false): elif n =0 then RETURN(true): elif n =1 then RETURN(false): fi; ppl := nextprime(n)-n ; pmi := n-prevprime(n) ; RETURN (isprime(min(ppl,pmi)) ) ; end: for n from 0 to 200 do if isA160666(n) then printf("%d,",n) ; fi; od: # R. J. Mathar, May 25 2009
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Mathematica
fQ[n_] := PrimeQ[ Min[ NextPrime[n] - n, n - NextPrime[n, -1]]]; Select[ Range[0, 174], !PrimeQ@ # && fQ@# &] (* Robert G. Wilson v, May 25 2009 *)
Extensions
More terms from R. J. Mathar and Robert G. Wilson v, May 25 2009
Comments