This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A173579 #8 Jun 25 2020 12:00:58 %S A173579 3,17,21,53,57,69,83,87,107,119,123,153,207,227,243,249,251,261,269, %T A173579 279,293,299,327,329,333,339,347,377,381,383,399,411,431,437,443,471, %U A173579 489,497,513,521,527,549,567,573,579,587,591,597,599,611,633,641,647,657 %N A173579 Natural numbers n which give primes when 1331 = 11^3 is prefixed. %C A173579 Concatenation of N = 1331 = 11^3 = palindrome(113) and natural n is a prime. No zeros "between" N and n. %C A173579 13 = emirp(1) = prime(6), R(13) = 31 = emirp(3) = prime(11). %C A173579 Necessarily n = 3 * k or n = 3 * k + 2, but not n = 3 * k + 1, because sod(1331) = 8. So no prime twins are terms of the sequence. %D A173579 Leonard E. Dickson: History of the Theory of numbers, vol. I, Dover Publications 2005 %D A173579 K. Haase, P. Mauksch: Spass mit Mathe, Urania-Verlag Leipzig, Verlag Dausien Hanau, 2. Auflage 1985 %D A173579 Theo Kempermann: Zahlentheoretische Kostproben, Harri Deutsch, 2. aktualisierte Auflage 2005 %H A173579 Harvey P. Dale, <a href="/A173579/b173579.txt">Table of n, a(n) for n = 1..1000</a> %e A173579 13313 = prime(1581) => a(1) = 3. %e A173579 133117 = prime(12425) => a(2) = 17. %e A173579 133103, 133109 are prime, but "0" included: "03" resp. "09" are no terms of the sequence. %t A173579 Select[Range[700],PrimeQ[1331*10^IntegerLength[#]+#]&] (* _Harvey P. Dale_, Jun 25 2020 *) %o A173579 (PARI) isok(n) = isprime(n + 1331*10^(length(Str(n)))); \\ _Michel Marcus_, Aug 27 2013 %Y A173579 A102006, A167535, A168147, A168219, A168274 %K A173579 base,nonn %O A173579 1,1 %A A173579 Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Feb 22 2010