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A014092
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Numbers that are not the sum of 2 primes.
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49
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1, 2, 3, 11, 17, 23, 27, 29, 35, 37, 41, 47, 51, 53, 57, 59, 65, 67, 71, 77, 79, 83, 87, 89, 93, 95, 97, 101, 107, 113, 117, 119, 121, 123, 125, 127, 131, 135, 137, 143, 145, 147, 149, 155, 157, 161, 163, 167, 171, 173, 177, 179, 185, 187, 189, 191, 197, 203, 205, 207, 209
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OFFSET
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1,2
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COMMENTS
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Suggested by the Goldbach conjecture that every even number larger than 2 is the sum of 2 primes.
Since (if we believe the Goldbach conjecture) all the entries > 2 in this sequence are odd, they are equal to 2 + an odd composite number (or 1).
Otherwise said, the sequence consists of 2 and odd numbers k such that k-2 is not prime. In particular there is no element from A006512, greater of a twin prime pair. - M. F. Hasler, Sep 18 2012
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REFERENCES
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G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 5th ed., Oxford Univ. Press, 1979, Section 2.8 (for Goldbach conjecture).
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LINKS
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FORMULA
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Odd composite numbers + 2 (essentially A014076(n) + 2 ).
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MAPLE
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g:=sum(sum(x^(ithprime(i)+ithprime(j)), i=1..j), j=1..50): gser:=series(g, x=0, 230): a:=proc(n) if coeff(gser, x^n)=0 then n else fi end: seq(a(n), n=1..225); # Emeric Deutsch, Apr 03 2006
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MATHEMATICA
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s1falsifiziertQ[s_]:= Module[{ip=IntegerPartitions[s, {2}], widerlegt=False}, Do[If[PrimeQ[ip[[i, 1]] ] ~And~ PrimeQ[ip[[i, 2]] ], widerlegt = True; Break[]], {i, 1, Length[ip]}]; widerlegt]; Select[Range[250], s1falsifiziertQ[ # ]==False&] (* Michael Taktikos, Dec 30 2007 *)
Join[{1, 2}, Select[Range[3, 300, 2], !PrimeQ[#-2]&]] (* Zak Seidov, Nov 27 2010 *)
Select[Range[250], Count[IntegerPartitions[#, {2}], _?(AllTrue[#, PrimeQ]&)]==0&] (* Harvey P. Dale, Jun 08 2022 *)
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PROG
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(PARI) isA014092(n)=local(p, i) ; i=1 ; p=prime(i); while(p<n, if( isprime(n-p), return(0)); i++; p=prime(i)); 1
n=1; for(a=1, 200, if(isA014092(a), print(n, " ", a); n++)) \\ R. J. Mathar, Aug 20 2006
(Haskell)
a014092 n = a014092_list !! (n-1)
a014092_list = filter (\x ->
all ((== 0) . a010051) $ map (x -) $ takeWhile (< x) a000040_list) [1..]
(Python)
from sympy import prime, isprime
def ok(n):
i=1
x=prime(i)
while x<n:
if isprime(n - x): return False
i+=1
x=prime(i)
return True
print([n for n in range(1, 301) if ok(n)]) # Indranil Ghosh, Apr 29 2017
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CROSSREFS
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Equivalent sequence for prime powers: A071331.
Numbers that can be expressed as the sum of two primes in k ways for k=0..10: this sequence (k=0), A067187 (k=1), A067188 (k=2), A067189 (k=3), A067190 (k=4), A067191 (k=5), A066722 (k=6), A352229 (k=7), A352230 (k=8), A352231 (k=9), A352233 (k=10).
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KEYWORD
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nonn,nice,easy
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AUTHOR
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STATUS
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approved
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