A162572 Decimal numbers n which, when converted to a lower number base, show the reversed digits of n.

1, 2, 3, 4, 5, 6, 7, 8, 13, 23, 46, 445, 2116, 15226, 313725, 1527465, 3454446, 2426472326, 3066511287, 102461381175475216

Offset

1,2

Comments

All entries lack the digit 9, because this digit is absent in the representations in bases 2 to 9.

The sequence is finite because for every n > 10^22 the representation of n in a base b < 10 has more digits than the representation of n in base 10. a(20) is the last term. - Giovanni Resta, Aug 13 2019

Links

Table of n, a(n) for n=1..20.

Example

13 is 31 in base 4. 23 is 32 in base 7. 46 is 64 in base 7.
801 is not a term since it is 1080 in base 9, so with an extra 0.

Prog

(PARI) isok(n) = {my(d = digits(n)); for (b=2, 9, my(rd = Vecrev(digits(n, b))); if ((#rd == #d) && fromdigits(rd) == n, return (b)); ); } \\ Michel Marcus, Aug 05 2019

Crossrefs

Cf. A034294, A090144. - R. J. Mathar, Jul 17 2009

Sequence in context: A200374 A033080 A090144 * A250476 A222260 A032991

Adjacent sequences: A162569 A162570 A162571 * A162573 A162574 A162575

Keyword

nonn,base,fini,full

Author

Claudio Meller, Jul 06 2009

Extensions

Keyword:base, single-digit numbers and 313725 added by R. J. Mathar, Jul 17 2009

a(16)-a(17) from Michel Marcus, Aug 05 2019

a(18)-a(19) from Giovanni Resta, Aug 06 2019

a(20) from Giovanni Resta, Aug 13 2019

Status

approved