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A216880
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Numbers of the form 3p - 2 where p and 6p + 1 are prime.
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1
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4, 7, 13, 19, 31, 37, 49, 67, 109, 139, 181, 217, 247, 301, 307, 319, 391, 409, 451, 517, 541, 697, 721, 769, 787, 811, 829, 847, 877, 931, 937, 991, 1039, 1099, 1117, 1189, 1327, 1381, 1399, 1507, 1669, 1729, 1777, 1801, 1819, 1921, 1957, 1981, 2047, 2179, 2251, 2281
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OFFSET
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1,1
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COMMENTS
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This formula produces many primes and semiprimes.
Taken just the terms from the sequence above:
n is prime for the following values of p: 3, 5, 7, 11, 13, 23, 37, 47, 61, 103, 137, 181, 257, 263, 271, 277, 293, 313, 331, 347, 373, 443, 461, 467, 557, 593, 601, 727, 751, 761.
n is a semiprime of the form (6*m + 1 )*(6*n + 1) for the following values of p: 73, 83, 101, 241, 367, 653, 661.
n is a semiprime of the form (6*m - 1 )*(6*n - 1) for the following values of p: 107, 131, 151, 173, 397, 503, 607, 641, 683.
n is the square of a prime for the following values of p: 2, 17.
n is an absolute Fermat pseudoprime for the following value of p: 577.
n is a product, not squarefree, of two primes for the following values of p: 283, 311.
Note: any number from the sequence is a term of one of the categories above.
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LINKS
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MATHEMATICA
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3#-2&/@Select[Prime[Range[200]], PrimeQ[6#+1]&] (* Harvey P. Dale, Mar 04 2023 *)
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PROG
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(MATLAB) p=primes(10000);
m=1;
for u=1:1000
if isprime(6*p(u)+1)==1
sol(m)=3*p(u)-2;
m=m+1;
end
end
(Magma) [3*p-2:p in PrimesUpTo(1000)| IsPrime(6*p+1)]; // Marius A. Burtea, Apr 10 2019
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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