A222820 a(n) is the number of reverse multipliers for base n.

1, 2, 2, 3, 3, 3, 5, 4, 3, 6, 5, 4, 7, 7, 4, 8, 6, 8, 8, 7, 6, 11, 11, 6, 8, 9, 6, 13, 12, 10, 13, 6, 9, 14, 10, 9, 13, 17, 9, 15, 12, 13, 17, 13, 11, 20, 16, 12, 12

Offset: 2

Author

N. J. A. Sloane, Mar 13 2013

Keywords

• nonn
• more
• base

Comments

If there is a number m such that the reversal of m in base n is c times m, then c is called a reverse multiplier for n. For example, 2 is a reverse multiplier for base n=5, since 8 (base 10) = 13 (base 5), and 2*8 = 16 (base 10) = 31 (base 5).

The trivial reverse multiplier 1 is included.

a(n)-1 is the length of row n of A222817. - Michel Marcus, Apr 12 2020

References

• For a complete list of references and links related to this problem see A214927.

Links

• N. J. A. Sloane, 2178 And All That, arXiv:1307.0453 [math.NT], 2013; see also, Fib. Quart., 52 (2014), 99-120.
• N. J. A. Sloane, 2178 And All That [Local copy]
• Anne Ludington Young, k-Reverse multiples, Fib. Q., 30 (1992), 126-132.

Crossrefs

Cf. A214927, A222817, A222818, A222819.

See A214927 for other cross-references.