Pete

sub FilterSeries {
    my( $base, $generations, @series ) = @_;

    my @newseries;

    my ( $next, $i, $j );
    for( $i = 1; $i < $generations; $i++) {
	if( $i <= $base ) {
	    $next = $i;
	}
	else {
	    $j = $i - $base;
	    $next = $base + ($j * $j);
	}
	#print "Nextval: $next\n";
	my @candidates;
	my $keeper;
	# Candidates for "next" backup are everything <= the next value
	while( @series && $series[0] <= $next ) {
	    push( @candidates, shift( @series ));
	}
	if( @candidates ) {
	    # Keep oldest one only
	    $keeper = pop( @candidates );
	    #print "Keep $keeper\n";
	    # Delete the rest
	    foreach my $cand ( @candidates ) {
		print "Delete $cand\n";
	    }
	    push( @newseries, $keeper );
	}
    }
    # Delete any leftover entries older than the max
    foreach my $cand ( @series ) {
	print "Delete off end: $cand\n";
    }
    return @newseries;
}