A082445 Palindromic primes with middle digit 9.

191, 797, 13931, 17971, 19991, 71917, 77977, 79997, 94949, 95959, 1129211, 1409041, 1469641, 1489841, 1579751, 1589851, 1609061, 1829281, 1879781, 1909091, 1969691, 3089803, 3319133, 3329233, 3439343, 3449443, 3479743, 3569653, 3589853, 3689863, 3709073, 3769673

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..611 (* All such primes with 9 or fewer digits *)

Mathematica

ppmd9Q[n_]:=Module[{idn=IntegerDigits[n]}, idn==Reverse[idn]&&idn[[(Length[ idn]+1)/2]]==9]; Flatten[Table[Select[Prime[Range[PrimePi[10^(2n)+1], PrimePi[ 10^(2n+1)-1]]], ppmd9Q], {n, 3}]] (* Harvey P. Dale, Feb 11 2015 *)

Prog

(Magma) [ p: p in PrimesUpTo(200000000) | IsOdd(d) and D[(d+1) div 2] eq 9 and D eq Reverse(D) where d is #D where D is Intseq(p) ]; // Vincenzo Librandi, Apr 12 2011

Crossrefs

Cf. A002385.

Sequence in context: A337791 A347294 A086878 * A108848 A052165 A103733

Adjacent sequences: A082442 A082443 A082444 * A082446 A082447 A082448

Keyword

nonn,base

Author

Lekraj Beedassy, Apr 25 2003

Extensions

a(4), a(14), a(18), a(24), a(27) from Vincenzo Librandi, Apr 12 2011

Status

approved