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A101985
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Numbers that occur only once in the count of primes between 2n and 3n.
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3
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11, 42, 93, 110, 113, 156, 186, 196, 197, 220, 252, 292, 298, 362, 403, 429, 493, 503, 609, 644, 659, 727, 735, 778, 790, 886, 888, 920, 932, 952, 953, 1008, 1023, 1024, 1079, 1093, 1094, 1100, 1109, 1136, 1165, 1208, 1212, 1213, 1226, 1238, 1250, 1311
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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MATHEMATICA
| f[n_] := PrimePi[3n] - PrimePi[2n]; t = Split[ Sort[ Table[ f[n], {n, 14000}] ]]; Flatten[ Select[t, Length[ # ] == 1 &]] (from Robert G. Wilson v Feb 10 2005)
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PROG
| (PARI) bet2n3n(n) = { local(c, c1, x, y); a=vector(10002); for(x=1, n, c=0; forprime(y=2*x+1, 3*x-1, c++; ); a[x] = c; ); b=vecsort(a); for(x=1, 10000, if(b[x]>0, if(b[x+1]<>b[x]&b[x+1]<>b[x+2], print1(b[x]+1", ") ); ); ) }
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CROSSREFS
| Sequence in context: A020452 A003356 A063152 * A055437 A055436 A062517
Adjacent sequences: A101982 A101983 A101984 * A101986 A101987 A101988
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KEYWORD
| easy,nonn
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AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Jan 29 2005
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 10 2005
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