OFFSET
1,1
COMMENTS
There are 4 semiprimes up to 10^1 {4, 6, 9, 10}. The differences between successive semiprimes are {2, 3, 1}. Thus a(1) = Max[ {2, 3, 1} ] = 3.
PROG
(PARI) A001358(prev)={ local(a=prev+1) ; while(bigomega(a)!=2, a++ ; ) ; return(a) ; } A123386(n)={ local(sp1=4, sp2=6, a=2) ; while(sp2<=10^n, a=max(a, sp2-sp1) ; sp1=sp2 ; sp2=A001358(sp1) ; ) ; return(a) ; } { for(n=1, 13, print(A123386(n)) ; ) ; } - 2 more term from R. J. Mathar, Jan 17 2008
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Nov 09 2006
EXTENSIONS
2 more term from R. J. Mathar, Jan 17 2008
a(8)-a(9) from Donovan Johnson, Sep 05 2008
a(10)-a(11) from Donovan Johnson, Apr 14 2010
a(12)-a(13) from Donovan Johnson, Sep 20 2012
STATUS
approved