A196509 Largest palindrome formed by using n single-digit numbers and the operators +, -, * and / where concatenation is not allowed.

9, 11, 343, 747, 6556, 65856, 405504, 4251524, 8847488

Offset

1,1

Comments

This puzzle is easily trivial if exponentiation or concatenation is allowed.

Best known results for a(10)..a(15) are 88499488, 846747648, 4095995904, 23613431632, 68899199886, 633498894336.

Erich Friedman solved and proved most of these terms.

Links

Table of n, a(n) for n=1..9.

Erich Friedman, Problem of the month June 1999

Example

11 = 9 + 2
343 = 7 * 7 * 7
747 = 9 * (9 * 9 + 2)
6556 = 9 * 9 * 9 * 9 - 5
65856 = 3 * 7 * 7 * 8 * 8 * 8
405504 = 8 * 8 * 8 * 8 * 9 * (9 + 2)
4251524 = 8 * 9 * 9 * 9 * 9 * 9 * 9 - 4
8847488 = 8 * 8 * (5 * 6 * 8 * 8 * 8 * 9 + 2)

Crossrefs

Cf. A002113.

Sequence in context: A146603 A159003 A352004 * A269026 A124606 A110647

Adjacent sequences: A196506 A196507 A196508 * A196510 A196511 A196512

Keyword

nonn,base,more

Author

Kausthub Gudipati, Oct 03 2011

Status

approved