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A339309
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Numbers k such that A228553(k) is twice a prime.
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2
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2, 5, 7, 8, 9, 10, 14, 16, 34, 53, 55, 83, 91, 140, 172, 180, 182, 187, 189, 242, 246, 254, 265, 288, 361, 398, 404, 421, 435, 490, 508, 559, 574, 623, 706, 727, 736, 747, 770, 773, 777, 984, 985, 1065, 1093, 1106, 1125, 1187, 1245, 1256, 1287, 1341, 1346, 1361, 1372, 1381, 1449, 1467, 1573, 1596
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(3) = 7 is a term because A228553(7) = 82 = 2*41 and 41 is prime.
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MAPLE
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f:= proc(n)
local S;
S:= select(t -> isprime(t) and isprime(2*n-t), [seq(i, i=3..n, 2)]);
add(t*(2*n-t), t=S)
end proc:
f(2):= 4:
filter:= proc(t) local v; v:= f(t); v::even and isprime(v) end proc:
select(filter, [$1..2000]);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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