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 A241487 Primes p such that p+6, p+666 and p+6666 are also prime. 1
 7, 53, 67, 157, 191, 311, 331, 347, 353, 373, 443, 563, 571, 641, 821, 823, 857, 941, 1033, 1087, 1123, 1283, 1423, 1607, 1621, 1873, 1997, 2011, 2137, 2333, 2383, 2543, 2657, 2677, 2797, 2957, 3301, 3511, 3607, 3671, 3691, 3797, 3847, 4133, 5113, 5147, 5231 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The constants in the definition (6, 666 and 6666) are concatenations of the digit 6. LINKS K. D. Bajpai, Table of n, a(n) for n = 1..10000 EXAMPLE a(2) = 53 is a prime: 53+6 = 59, 53+666 = 719 and 53+6666 = 6719 are also prime. a(3) = 67 is a prime: 67+6 = 73, 67+666 = 733 and 67+6666 = 6733 are also prime. MAPLE KD:= proc() local a, b, d, e; a:= ithprime(n); b:=a+2; d:=a+222; e:=a+2222; if isprime(b)and isprime(d)and isprime(e)  then return (a) :fi; end: seq(KD(), n=1..5000); MATHEMATICA KD = {}; Do[p = Prime[n]; If[PrimeQ[p + 6] && PrimeQ[p + 666] && PrimeQ[p + 6666], AppendTo[KD, p]], {n, 5000}]; KD (*For the b-file*) c = 0; p = Prime[n]; Do[If[PrimeQ[p + 6] && PrimeQ[p + 666] && PrimeQ[p + 6666], c = c + 1; Print[c, "  ", p]], {n, 1, 2*10^6}]; PROG (PARI) s=[]; forprime(p=2, 6000, if(isprime(p+6) && isprime(p+666) && isprime(p+6666), s=concat(s, p))); s \\ Colin Barker, Apr 25 2014 CROSSREFS Cf. A000040, A023200, A046136, A230223, A236302, A236304, A237890, A241485. Sequence in context: A300875 A301485 A224501 * A236688 A239941 A253123 Adjacent sequences:  A241484 A241485 A241486 * A241488 A241489 A241490 KEYWORD nonn AUTHOR K. D. Bajpai, Apr 23 2014 STATUS approved

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Last modified August 13 22:57 EDT 2020. Contains 336473 sequences. (Running on oeis4.)