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 A101983 Numbers that are not a count of primes between 2n and 4n. 3
 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; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 11 is the first number that does not equal a count of primes between 2n and 4n. MATHEMATICA 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) PROG (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", ") ) ); ) } CROSSREFS Complement of A101947. Sequence in context: A030054 A225896 A140542 * A139953 A111067 A172067 Adjacent sequences:  A101980 A101981 A101982 * A101984 A101985 A101986 KEYWORD easy,nonn AUTHOR Cino Hilliard (hillcino368(AT)gmail.com), Jan 28 2005 EXTENSIONS More terms from Robert G. Wilson v, Feb 10 2005 STATUS approved

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