A100026 Consider all (2n+1)-digit palindromic primes of the form 10...0M0...01 (so that M is a palindrome with <= 2n-1 digits); a(n) = smallest such M.

0, 3, 3, 3, 5, 8, 323, 5, 8, 212, 3, 161, 8, 3, 242, 3, 8, 10901, 737, 161, 242, 333, 282, 6, 252, 474, 5, 12921, 8, 131, 18381, 6, 444, 6, 797, 606, 717, 15351, 464, 333, 626, 545, 13031, 161, 747, 191, 323, 636, 32523, 303, 282, 888, 686, 18981, 111, 15951, 12021

Offset

1,2

Comments

Is this the same as "Longest palindromic proper substring of A100027(n) or A028989(n+1) that occurs only once in the decimal representation of A100027(n) or A028989(n+1), respectively"? - Felix Fröhlich, Apr 30 2022

Links

Chai Wah Wu, Table of n, a(n) for n = 1..1000

Mathematica

f[n_] := Block[{k = 0, t = Flatten[Join[{1}, Table[0, {n - 1}]]]}, While[s = Drop[t, Min[ -Floor[ Log[10, k]/2], 0]]; k != FromDigits[ Reverse[ IntegerDigits[k]]] || !PrimeQ[ FromDigits[ Join[s, IntegerDigits[k], Reverse[s]]]], k++ ]; k]; Table[ f[n], {n, 56}] (* Robert G. Wilson v, Nov 22 2004 *)

Crossrefs

The corresponding palindromic primes are shown in A100027.

Cf. A028989, A099744, A099746, A100028.

Sequence in context: A141695 A358452 A261450 * A350537 A367555 A100049

Adjacent sequences: A100023 A100024 A100025 * A100027 A100028 A100029

Keyword

nonn,base

Author

Harvey Dubner (harvey(AT)dubner.com), Nov 20 2004

Extensions

More terms from Robert G. Wilson v, Nov 22 2004

Status

approved