A080357 Smallest x such that between x and 2x exactly n twin prime numbers can be found.

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

Links

Table of n, a(n) for n=1..49.

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

Cf. A001359, A080356.

Sequence in context: A072291 A325500 A084191 * A064032 A118443 A355236

Adjacent sequences: A080354 A080355 A080356 * A080358 A080359 A080360

Keyword

nonn

Author

Labos Elemer, Feb 19 2003

Status

approved