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A246808
Palindromic terms of the sequence A245317.
1
2112, 4803443084, 6992662996, 180461164081, 214591195412, 409473374904, 563715517365, 4163019339103614, 1050417996997140501
OFFSET
1,1
COMMENTS
For each n, A100414(n).reversal(A100414(n)) is in the sequence, where dot denotes concatenation. What is the first term of the sequence which is not of the above form?
a(9) <= 253385633342243336583352 and a(10) <= 661494322636636223494166.
a(9) = A245317(997140501) = 1050417996997140501 is the smallest term of the sequence which is not of the form A100414(n).reversal(A100414(n)). 253385633342243336583352 and 661494322636636223494166 are two consecutive terms of the sequence. - Farideh Firoozbakht, Sep 23 2014
FORMULA
For n<9, a(n) = A100414(n).reversal(A100414(n)).
MATHEMATICA
h[n_]:=If[!PrimeQ[n], FromDigits[Flatten[{IntegerDigits[n], IntegerDigits[n-PrimePi[n]-1]}]]]; Do[a=h[n]; If[!PrimeQ[n]&&FromDigits[Reverse[IntegerDigits[a]]]==a, Print[a]], {n, 100000000}]
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Jahangeer Kholdi, Sep 17 2014
EXTENSIONS
a(9) from Farideh Firoozbakht, Sep 23 2014
STATUS
approved