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A043053
a(n) = (s(n) + 1)/5, where s(n) = n-th base-5 palindrome that starts with 4.
1
1, 5, 21, 22, 23, 24, 25, 101, 107, 113, 119, 125, 501, 506, 511, 516, 521, 527, 532, 537, 542, 547, 553, 558, 563, 568, 573, 579, 584, 589, 594, 599, 605, 610, 615, 620, 625, 2501, 2531, 2561, 2591, 2621, 2627, 2657, 2687, 2717
OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..937 (all terms up to 5 million)
MATHEMATICA
b5s4Q[n_]:=Module[{idn5=IntegerDigits[n, 5]}, idn5[[1]]==4&&idn5 == Reverse[ idn5]]; (#+1)/5&/@Select[Range[30000], b5s4Q] (* Harvey P. Dale, Jun 22 2022 *)
CROSSREFS
Sequence in context: A355036 A263130 A165204 * A004163 A350328 A113410
KEYWORD
nonn,base
STATUS
approved