A214426 Numbers n palindromic in exactly four bases b, 2 <= b <= 10.

8, 121, 373, 786435

Offset

1,1

Comments

Searched up to 10^18. Rick Regan mentions these four numbers, also found by Bill Beckmann, at the end of his webpage. - T. D. Noe, Aug 18 2012

Links

Table of n, a(n) for n=1..4.

Rick Regan, Finding numbers that are palindromic in multiple bases

Formula

A050812(n) = 4.

Example

8 is palindromic in bases 3, 7, 9, and 10.
121 is palindromic in bases 3, 7, 8, and 10.
373 is palindromic in bases 4, 7, 9, and 10.
786435 is palindromic in bases 2, 4, 7, and 8.

Mathematica

n = -1; t = {}; While[Length[t] < 4, n++; If[Count[Table[s = IntegerDigits[n, m]; s == Reverse[s], {m, 2, 10}], True] == 4, AppendTo[t, n]]]; t

Crossrefs

Cf. A050813, A214423, A214424, A214425 (palindromic in 0-3 bases).

Sequence in context: A173774 A034669 A000848 * A281833 A299077 A298997

Adjacent sequences: A214423 A214424 A214425 * A214427 A214428 A214429

Keyword

nonn,base,hard

Author

T. D. Noe, Jul 18 2012

Status

approved