OFFSET
1,1
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 1...225
EXAMPLE
a(2) = 6 because that is the largest semiprime < 2*a(1) = 8, where a(1) is the first semiprime.
a(3) = 10, the largest semiprime < 2*6 = 12.
MATHEMATICA
PrevSemiPrime[n_, k_] := Block[{c = 0, sp = n - 1}, While[c < k, While[ PrimeOmega[sp] != 2, sp--]; sp--; c++]; sp + 1]; NestList[ PrevSemiPrime[ 2#, 1] &, 4, 34] (* Robert G. Wilson v, Oct 19 2012 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jonathan Vos Post, Oct 19 2012
EXTENSIONS
Terms greater than a(15) from Robert G. Wilson v, Oct 19 2012
STATUS
approved