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A103804
Primes p such that both 2p +/- 21 are primes.
2
13, 19, 29, 31, 41, 59, 79, 89, 101, 109, 131, 179, 211, 239, 241, 271, 311, 331, 349, 409, 421, 449, 499, 509, 521, 541, 601, 619, 701, 751, 821, 839, 881, 1009, 1091, 1181, 1201, 1319, 1321, 1399, 1429, 1459, 1489, 1531, 1571, 1619, 1801, 1949, 1951
OFFSET
1,1
FORMULA
p, 2p-21 and 2p+21 all are positive primes.
MATHEMATICA
Select[Range[2000], PrimeQ[ # ] && PrimeQ[2# + 21] && PrimeQ[2# - 21] &]
Select[Prime[Range[4, 500]], And@@PrimeQ[2#+{21, -21}]&] (* Harvey P. Dale, Dec 18 2012 *)
CROSSREFS
Sequence in context: A227092 A123840 A258589 * A063640 A092104 A281483
KEYWORD
nonn
AUTHOR
Zak Seidov, Feb 16 2005
STATUS
approved