A262873 Predestined numbers A262743 in which every term is generated by at least one pair of products where all (and only those) first product's factor's digits are, in reverse order, the same as those of the second two factors.

504, 756, 806, 868, 1008, 1148, 1176, 1209, 1472, 1475, 1512, 1638, 1708, 2016, 2184, 2208, 2418, 2548, 2730, 2772, 2924, 3024, 3388, 4416

Offset: 1

Author

Francesco Di Matteo, Oct 03 2015

Keywords

• nonn
• base

Comments

In this sequence, the position of the multiplication sign in the reversed order is irrelevant, so, e.g., 11088 (48*231 and 132*84), 1176 (4*294 and 49*24) and 2548 (4*637 and 7*364) are in the sequence.

Examples

			504  = 12*42 = 24*21;
756  = 12*63 = 36*21;
806  = 13*62 = 26*31;
868  = 4*217 = 7*124;
1008 = 12*84 = 48*21;
1148 = 14*82 = 28*41;
1176 = 4*294 = 49*24, etc.
		

References

• Francesco Di Matteo, Sequenze ludiche, Game Edizioni (2015), page 34.

Links

• Francesco Di Matteo, Table of n, a(n) for n = 1..132
• Algebra.com, Question 265287
• A. Marchini and F. Di Matteo, All the first 132 terms calculated
• Math Forum at Drexel, Reversing the Digits

Crossrefs

Subsequence of A262743.

Cf. A228164 (contains only symmetrical digits' factors)