A246808 Palindromic terms of the sequence A245317.

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

Links

Table of n, a(n) for n=1..9.

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

Cf. A002808, A004086, A100414, A245317.

Sequence in context: A046382 A168662 A107528 * A217439 A365240 A067632

Adjacent sequences: A246805 A246806 A246807 * A246809 A246810 A246811

Keyword

nonn,base,more

Author

Jahangeer Kholdi, Sep 17 2014

Extensions

a(9) from Farideh Firoozbakht, Sep 23 2014

Status

approved