protected static Sequence getSequence(String expression) {
int start = 0, add = 2, max = -1, modVal = -1;
JsRegexp expressionRegExp = new JsRegexp(
"^((odd|even)|([1-9]\\d*)|((([1-9]\\d*)?)n((\\+|\\-)(\\d+))?)|(\\-(([1-9]\\d*)?)n\\+(\\d+)))$");
JsObjectArray<String> pseudoValue = expressionRegExp.exec(expression);
if (!truth(pseudoValue)) {
return null;
} else {
if (truth(pseudoValue.get(2))) { // odd or even
start = (eq(pseudoValue.get(2), "odd")) ? 1 : 2;