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A080357
Smallest x such that between x and 2x exactly n twin prime numbers can be found.
0
2, 3, 36, 54, 90, 96, 99, 135, 174, 330, 411, 414, 516, 531, 546, 651, 714, 726, 741, 744, 804, 936, 939, 966, 975, 999, 1014, 1071, 1134, 1170, 1191, 1365, 1395, 1401, 1650, 1665, 1686, 1695, 1764, 1770, 1779, 1836, 1926, 2010, 2025, 2064, 2079, 2136, 2211
OFFSET
1,1
FORMULA
a(n)=Min[x; A080356(x)=n]
EXAMPLE
n=7: first seven twin primes counted between 99 and 198: {101,107,137,149,179,191,197}.
MATHEMATICA
f[x_] := Count[Table[PrimeQ[j]&&PrimeQ[j+2], {j, x, 2*x}], True] t=Table[0, {100}]; Do[s=f[n]; If[s<101&&t[[s]]==0, t[[s]]=n], {n, 1, 10000}]; t
CROSSREFS
Sequence in context: A072291 A325500 A084191 * A064032 A118443 A355236
KEYWORD
nonn
AUTHOR
Labos Elemer, Feb 19 2003
STATUS
approved