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Search: id:A007510
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| A007510 |
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Single (or isolated or non-twin) primes.
(Formerly M2130)
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+0
71
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| 2, 23, 37, 47, 53, 67, 79, 83, 89, 97, 113, 127, 131, 157, 163, 167, 173, 211, 223, 233, 251, 257, 263, 277, 293, 307, 317, 331, 337, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 439, 443, 449, 457, 467, 479, 487, 491, 499, 503, 509, 541, 547, 557, 563
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Primes p such that neither p-2 nor p+2 is prime.
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Richard L. Francis, "Isolated Primes", J. Rec. Math., 11 (1978), 17-22.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
O. E. Pol, Determinacion geometrica de los numeros primos y perfectos.
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MAPLE
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with(numtheory): for i from 1 to 150 do p:=ithprime(i): if(not isprime(p+2) and not isprime(p-2)) then printf("%d, ", p) fi od: (Pab Ter)
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MATHEMATICA
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Transpose[Select[Partition[Prime[Range[100]], 3, 1], #[[2]] - #[[1]] != 2 && #[[3]] - #[[2]] != 2 &]][[2]] - Harvey P. Dale Mar 01 2001
Select[Prime[Range[4, 100]], !PrimeQ[ #-2]&&!PrimeQ[ #+2]&] (* Zak Seidov May 07 2007 *)
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PROGRAM
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UBASIC: 10 'primes using counters 20 N=3:print "2 "; :print "3 "; :C=2 30 A=3:S=sqrt(N) 40 B=N\A 50 if B*A=N then 55 55 Q=N+2:R=N-2: if Q<>prmdiv(Q) and N=prmdiv(N) and R<>prmdiv(R) then print Q; N; R; "-"; :stop:else N=N+2:goto 30 60 A=A+2 70 if A<=sqrt(N) then 40:stop 81 C=C+1 100 N=N+2:goto 30 - Enoch Haga (Enokh(AT)comcast.net), Oct 08 2007
(PARI) forprime(x=2, 1000, if(!isprime(x-2)&&!isprime(x+2), print(x))) [From Zak Seidov (zakseidov(AT)yahoo.com), Mar 23 2009]
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CROSSREFS
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Cf. A083370 A124582 A134099 A134100 A134101.
Sequence in context: A049580 A061448 A115233 this_sequence A117242 A144550 A106736
Adjacent sequences: A007507 A007508 A007509 this_sequence A007511 A007512 A007513
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KEYWORD
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nonn,easy,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Robert G. Wilson v (rgwv(AT)rgwv.com)
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EXTENSIONS
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More terms from Pab Ter (pabrlos2(AT)yahoo.com), Nov 11 2005
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