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A126071 Number of bases (2 <= b <= n+1) in which n is a palindrome. 4
1, 1, 2, 2, 3, 2, 3, 3, 3, 4, 2, 3, 3, 3, 4, 4, 4, 4, 2, 4, 5, 3, 3, 5, 3, 5, 4, 5, 3, 4, 4, 4, 4, 4, 3, 6, 3, 4, 3, 6, 3, 5, 3, 4, 5, 5, 2, 6, 3, 5, 5, 6, 2, 5, 5, 5, 5, 3, 3, 7, 3, 4, 6, 5, 6, 5, 4, 5, 3, 5, 3, 7, 4, 4, 4, 4, 3, 7, 2, 8, 4, 5, 3, 7, 6, 4, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
a(n) >= 1, since n will always have a single "digit" in base n+1.
LINKS
EXAMPLE
From bases 2 to 9 respectively, 8 can be represented as: 1000, 22, 20, 13, 12, 11, 10, 8. Three of those are symmetrical (22, 11, 8) and so a(8) = 3.
MATHEMATICA
Table[cnt = 0; Do[d = IntegerDigits[n, k]; If[d == Reverse[d], cnt++], {k, 2, n + 1}]; cnt, {n, 100}] (* T. D. Noe, Oct 04 2012 *)
PROG
(PARI) a(n) = sum(k=2, n+1, d = digits(n, k); Vecrev(d) == d); \\ Michel Marcus, Mar 07 2015
CROSSREFS
Cf. A016026.
Cf. A016038, A047811 (related to numbers having 2 bases).
Sequence in context: A334686 A057941 A358550 * A338292 A359728 A217865
KEYWORD
nonn,base
AUTHOR
Paul Richards, Mar 01 2007
EXTENSIONS
Extended by T. D. Noe, Oct 04 2012
STATUS
approved

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Last modified May 20 01:45 EDT 2024. Contains 372703 sequences. (Running on oeis4.)