
EXAMPLE

The first term > 0 is 902, and we see that 902 is indeed an envelope number as 0 is a multiple of 92; as we want always to insert an envelope number into the biggest next possible envelope, we try first 909, but 909 has no 2digit divisor; nor could we select 908 (for the same reason), nor 907 (as 907 is prime), nor 906 (as 906 too has no 2digit divisor), nor 905 or 904 (for the same reason), nor 903 (as 903 would produce the envelope number 29031 which has itself no 2digit divisor); 902 is ok as 902 has two 2digit divisors, 11 and 22: we thus keep the biggest one (22) to build a(3) = 29022; a(3) has itself three 2digit divisors, 14, 21 and 42: we keep the biggest one to build a(4) = 4290222; this number has 16 divisors altogether, but three of them are 2digit numbers, 17, 34 and 51; we will keep 34 (as 51 cannot produce an infinite sequence) to build a(5) = 342902224, etc.
A way to spare some space in presenting this sequence, would be to align, after a(1) = 0, the successive divisors that are kept; this would form the sequence 0,92,22,42,34,14,66,18,36,54,72,18,63,57,33,89,47,11,21,43,59,47,79,67,61,43,27,27,99,81,19,17,63,27,99,27,27,93,71,59,11,49,11,69,87,39,79,79,91,33,39,43,53,43,11,93,27,51,57,81,81,97,29,99,91,37,37,21,33,69,63,33,39,23,61,51,27,33,23,73,11,67,99,27,27,69,...
