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 A181450 #17 Dec 21 2024 14:21:43 %S A181450 10,21,23,34,43,65,76,89,109,111,197,199,241,351,485,769,881,1079, %T A181450 6049,19601 %N A181450 Numbers k such that 11 is the largest prime factor of k^2 - 1. %C A181450 Numbers k such that A076605(k) = 11. %C A181450 Sequence is finite and complete, for proof see A175607. %C A181450 Search for terms can be restricted to the range from 2 to A175607(5) = 19601; primepi(11) = 5. %t A181450 Select[Range[20000], FactorInteger[#^2-1][[-1, 1]]==11&] %o A181450 (Magma) [ n: n in [2..20000] | m eq 11 where m is D[#D] where D is PrimeDivisors(n^2-1) ]; // _Klaus Brockhaus_, Feb 18 2011 %o A181450 (PARI) is(n)=n=n^2-1; forprime(p=2, 7, n/=p^valuation(n, p)); n>1 && 11^valuation(n, 11)==n \\ _Charles R Greathouse IV_, Jul 01 2013 %Y A181450 Row 5 of A223701. %Y A181450 Cf. A076605, A175607, A181447-A181449, A181451-A181470, A181568. %K A181450 fini,full,nonn %O A181450 1,1 %A A181450 _Artur Jasinski_, Oct 21 2010