A222727 -id:A222727 - cp's OEIS frontend

A043042 Base-10 palindromes that start with 7.

7, 77, 707, 717, 727, 737, 747, 757, 767, 777, 787, 797, 7007, 7117, 7227, 7337, 7447, 7557, 7667, 7777, 7887, 7997, 70007, 70107, 70207, 70307, 70407, 70507, 70607, 70707, 70807, 70907, 71017, 71117, 71217, 71317, 71417, 71517, 71617, 71717, 71817, 71917

Offset: 1

Clark Kimberling

Subsequence of A002113 (palindromic numbers). Union of A222727 (palindromic primes starting with a digit 7) and A222728 (palindromic composite numbers starting with a digit 7). - Jaroslav Krizek, Mar 12 2013

Jaroslav Krizek, Table of n, a(n) for n = 1..2222

Cf. A002113.

palQ[n_Integer, base_Integer] := Module[{idn = IntegerDigits[n, base]}, idn == Reverse[idn]]; Select[Range[0, 100000], IntegerDigits[#][[1]] == 7 && palQ[#, 10] &] (* T. D. Noe, Mar 12 2013 *)
Select[Range[72000],First[IntegerDigits[#]]==7&&PalindromeQ[#]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 02 2018 *)

A222728 Palindromic composite numbers starting with a digit 7.

Original entry on oeis.org

77, 707, 717, 737, 747, 767, 777, 7007, 7117, 7227, 7337, 7447, 7557, 7667, 7777, 7887, 7997, 70007, 70107, 70307, 70407, 70707, 70807, 70907, 71017, 71117, 71217, 71417, 71517, 71617, 71717, 71817, 72027, 72127, 72327, 72427, 72527, 72627, 72827, 72927, 73137

Offset: 1

Jaroslav Krizek, Mar 09 2013

Subsequence of A032350 (palindromic nonprime numbers) and A002113 (palindromic numbers). Complement of A222727 (palindromic primes starting with a digit 7) with respect to A043042 (palindromic numbers starting with a digit 7).

Jaroslav Krizek, Table of n, a(n) for n = 1..1038

Cf. A032350, A002113, A222727, A043042.

Table[Select[Range[7*10^d,8*10^d-1],CompositeQ[#]&&PalindromeQ[#]&],{d,4}]//Flatten (* Harvey P. Dale, Nov 07 2021 *)

cp's OEIS Frontend

A043042 Base-10 palindromes that start with 7.

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