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 A153519 #14 Mar 19 2020 06:12:06 %S A153519 1,6,9,10,15,18,30,33,45,55,90,91,99,165,246,259,370,385,451,481,495, %T A153519 505,657,703,715,909,1035,1045,1233,1626,2035,2409,2981,3333,3367, %U A153519 3585,4005,4141,4187,4521,4545,5005,5461,6533,6541,6565,7107,7471,7777,8149 %N A153519 Nonprime numbers k such that 10^k == 10 (mod k) and are not Carmichael numbers. %C A153519 Old name: Members of A121014 which are not Carmichael numbers A002997. %H A153519 Amiram Eldar, <a href="/A153519/b153519.txt">Table of n, a(n) for n = 1..10000</a> %t A153519 Select[Range[8000], !PrimeQ[#] && PowerMod[10, #, #] == Mod[10, #] && !(# > 1 && Divisible[# - 1, CarmichaelLambda[#]]) &] (* _Amiram Eldar_, Mar 19 2020 *) %o A153519 (PARI) isok(n) = !isprime(n) && !is_A002997(n) && (Mod(10^n, n) == Mod(10, n)); \\ _Michel Marcus_, Nov 06 2013 %Y A153519 Cf. A002997, A122780, A153508, A153513, A153514, A153515. %K A153519 nonn %O A153519 1,2 %A A153519 _Artur Jasinski_, Dec 28 2008 %E A153519 New name from _Michel Marcus_, Nov 06 2013