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Isolated prime difference equals 6: primes prime(k) such that d(k) = prime(k+1) - prime(k) = 6 but neither d(k+1) nor d(k-1) is 6.
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%I #24 Mar 22 2020 05:47:36

%S 23,31,61,73,83,131,233,271,331,353,383,433,443,503,541,571,677,751,

%T 991,1013,1033,1063,1231,1283,1291,1321,1433,1453,1493,1543,1553,1601,

%U 1613,1621,1657,1777,1861,1973,1987,2011,2063,2131,2207,2333,2341,2351

%N Isolated prime difference equals 6: primes prime(k) such that d(k) = prime(k+1) - prime(k) = 6 but neither d(k+1) nor d(k-1) is 6.

%C Consecutive primes 17, 19, 23, 29, 31 give the pattern of first differences 2, 4, 6, 2 in which the neighboring differences of 6 are not equal to 6.

%C a(n) - 6 can be prime but not the prime immediately previous to a(n); e.g., 23 - 6 = 17, but the prime 19 lies between the two primes 17 and 23.

%H Robert Israel, <a href="/A052160/b052160.txt">Table of n, a(n) for n = 1..10000</a>

%p N:= 3000: # to get all terms <= N

%p Primes:= select(isprime, [seq(i,i=3..N,2)]):

%p d:= Primes[2..-1]-Primes[1..-2]:

%p R:= select(t -> d[t] = 6 and d[t+1] <> 6 and d[t-1] <> 6, [$2..nops(d)-1]):

%p Primes[R]; # _Robert Israel_, May 29 2018

%o (PARI) lista(nn) = {vp = primes(nn); vd = vector(#vp-1, k, vp[k+1] - vp[k]); for (i=2, #vd, if ((vd[i] == 6) && (vd[i-1] !=6) && (vd[i+1] != 6), print1(vp[i], ", ")););} \\ _Michel Marcus_, May 29 2018

%Y Cf. A001223, A033451, A047948.

%K nonn

%O 1,1

%A _Labos Elemer_, Jan 25 2000