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

Author

Labos Elemer, Feb 19 2003

Keywords

• nonn

Examples

			n=7: first seven twin primes counted between 99 and 198: {101,107,137,149,179,191,197}.
		

Crossrefs

Cf. A001359, A080356.

Programs

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

Formula

a(n)=Min[x; A080356(x)=n]