A100957 - OEIS

A100957

Consider all (2n+1)-digit palindromic primes of the form 90...0M0...09 (so that M is a palindrome with <= 2n-1 digits); a(n) = smallest such M.

1, 7, 2, 1, 2, 5, 838, 232, 121, 8, 151, 202, 2, 101, 646, 5, 1, 151, 424, 404, 242, 131, 646, 272, 16361, 1, 494, 1, 868, 101, 494, 12421, 14041, 151, 595, 383, 515, 19091, 10001, 242, 17171, 20602, 161, 292, 11011, 8, 1, 11611, 22822, 232, 17771, 616, 767

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OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..200

MATHEMATICA

f[n_] := Block[{k = 0, t = Flatten[ Join[{9}, 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, 55}]

CROSSREFS

Cf. A100026, A100955, A100956.

Sequence in context: A197184 A089129 A387175 * A372907 A191856 A220862

Adjacent sequences: A100954 A100955 A100956 * A100958 A100959 A100960

KEYWORD

base,nonn

AUTHOR

Robert G. Wilson v, Nov 23 2004

STATUS

approved