A099051 - OEIS

%I #10 Jul 29 2015 01:15:24

%S 7,23,159,895,22527,106495,2228223,9961471,192937983,15569256447,

%T 66571993087,5085241278463,90159953477631,378231999954943,

%U 6614661952700415,477381560501272575,34011184385901985791

%N p*2^p - 1 where p is prime.

%C This is the subset of Woodall numbers of prime index. The 9th largest known Woodall prime is in this sequence: 12379*2^12379-1, where 12379 is prime, as found by Wilfrid Keller in 1984. Smaller primes are when p = 2, 3, 751. These numbers can also be semiprime, as when p = 159, 163, or 211 and hard to factor as when n = 349 (108 digits). - _Jonathan Vos Post_, Nov 19 2004

%D Ribenboim, P. The New Book of Prime Number Records. New York: Springer-Verlag, pp. 360-361, 1996

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/WoodallNumber.html">Woodall Numbers</a>.

%e If p=3, 3*2^3 - 1 = 23.

%e If p=11, 11*2^11 - 1 = 22527.

%t Table[ Prime[n]*2^Prime[n] - 1, {n, 17}] (* _Robert G. Wilson v_, Nov 16 2004 *)

%Y Similar to Woodall numbers (A003261). Cf. A002234.

%K nonn,easy

%O 1,1

%A _Parthasarathy Nambi_, Nov 13 2004

%E More terms from _Robert G. Wilson v_, Nov 15 2004