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Search: id:A101983
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| A101983 |
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Numbers that are not a count of primes between 2n and 4n. |
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+0
4
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| 11, 79, 134, 184, 186, 215, 245, 262, 284, 305, 387, 544, 694, 700, 706, 776, 814, 881, 939, 974, 1002, 1027, 1079, 1104, 1133, 1146, 1184, 1193, 1207, 1354, 1387, 1415, 1441, 1495, 1574, 1587, 1608, 1662, 1690, 1801, 1915, 1987, 2054, 2067, 2104, 2170
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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11 is the first number that does not equal a count of primes between 2n and 4n.
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MATHEMATICA
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f[n_] := PrimePi[4n] - PrimePi[2n]; t = Union[ Table[ f[n], {n, 12000}]]; Complement[ Range[ t[[ -1]]], t] (from Robert G. Wilson v Feb 10 2005)
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PROGRAM
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(PARI) bet2n4n(n) = { local(c, c1, x, y); a=vector(10001); for(x=1, n, c=0; forprime(y=2*x+1, 4*x-1, c++; ); a[x] = c; ); b=vecsort(a); for(x=1, 10000, if(b[x]>0, if(b[x+1]-b[x]>1, print1(b[x]+1", ") ) ); ) }
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CROSSREFS
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Complement of A101947.
Sequence in context: A041224 A030054 A140542 this_sequence A139953 A111067 A026841
Adjacent sequences: A101980 A101981 A101982 this_sequence A101984 A101985 A101986
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Jan 28 2005
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 10 2005
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