A222819 - OEIS

A222819

a(n) = number of nontrivial reverse multipliers for base n.

0, 1, 1, 2, 2, 2, 4, 3, 2, 5, 4, 3, 6, 6, 3, 7, 5, 7, 7, 6, 5, 10, 10, 5, 7, 8, 5, 12, 11, 9, 12, 5, 8, 13, 9, 8, 12, 16, 8, 14, 11, 12, 16, 12, 10, 19, 15, 11, 11, 9, 10, 19, 18, 17, 18, 13, 9, 23, 14, 15, 21, 19, 14, 19, 12, 18, 16, 19, 17, 26, 17, 11, 20, 16, 15, 21, 13, 26, 24, 13

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OFFSET

2,4

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 excluded.

LINKS

N. J. A. Sloane, Table of n, a(n) for n = 2..100

N. J. A. Sloane, 2178 And All That, Fib. Quart., 52 (2014), 99-120.

Anne Ludington Young, k-Reverse multiples, Fib. Q., 30 (1992), 126-132.

CROSSREFS

Cf. A214927, A222817, A222818, A222820.

See A214927 for other cross-references.

Sequence in context: A121806 A056944 A283681 * A194319 A208609 A249030

Adjacent sequences: A222816 A222817 A222818 * A222820 A222821 A222822

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, Mar 13 2013

STATUS

approved