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A081091
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Primes of the form 2^i + 2^j + 1, i>j>0.
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9
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7, 11, 13, 19, 37, 41, 67, 73, 97, 131, 137, 193, 521, 577, 641, 769, 1033, 1153, 2053, 2081, 2113, 4099, 4129, 8209, 12289, 16417, 18433, 32771, 32801, 32833, 40961, 65539, 133121, 147457, 163841, 262147, 262153, 262657, 270337, 524353, 524801
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| A000120(a(n))=3.
This is sequence A070739 without the Fermat primes, A000215. Sequence A081504 lists the i for which there are no primes. - T. D. Noe, Jun 22 2007
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
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EXAMPLE
| 13 = 2^3 + 2^2 + 1, therefore 13 is a term.
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MATHEMATICA
| Select[Flatten[Table[2^i + 2^j + 1, {i, 21}, {j, i-1}]], PrimeQ] (* From Alonso del Arte, Jan 11 2011 *)
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PROG
| (PARI)N=41; B(x)={nB=floor(log(x)/log(2)); z=0;
for(i=0, nB, if(bittest(x, i), z++; if(z>3, return(0); ); ); );
if(z == 3, return(1); , return(0); ); };
x=6; while(N, x=nextprime(x); if(B(x), print1(x, ", "); N--; ); x++; ); [W. Bomfim webonfim(AT)bol.com Jan 11, 2011]
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CROSSREFS
| Cf. A000040, A000215, A081092.
Essentially the same as A070739.
Cf. A095077 (primes with four bits set)
Sequence in context: A059308 A075521 A084444 * A027901 A129213 A110966
Adjacent sequences: A081088 A081089 A081090 * A081092 A081093 A081094
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KEYWORD
| nonn,easy
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 05 2003
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