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 A053339 #19 Jun 01 2018 04:21:01 %S A053339 255,435,455,561,595,665,705,795,805,885,957,1001,1105,1295,1309,1335, %T A053339 1463,1495,1551,1605,1615,1645,1729,1749,1855,1885,1947,1955,2001, %U A053339 2055,2065,2091,2093,2185,2235,2345,2387,2405,2465,2555,2703,2717,2755,2821 %N A053339 Squarefree terms of A050530 with 3 prime divisors. %H A053339 G. C. Greubel, <a href="/A053339/b053339.txt">Table of n, a(n) for n = 1..10000</a> %F A053339 Numbers k = pqr such that A051953(k) = k - EulerPhi(k) is a prime of polynomial form pq + pr + qr - p - q - r + 1. %e A053339 435 = 3*5*29 and 435 - Phi(435) = 3*5 + 3*29 + 5*29 - 3 - 5 - 29 + 1 = 211, the 47th prime. [corrected by _Jon E. Schoenfield_, May 30 2018] %t A053339 Select[Select[Range[3000],PrimeQ[#-EulerPhi[#]]&],SquareFreeQ[3] && PrimeOmega[#]==3&] (* _Harvey P. Dale_, Jun 23 2013 *) %o A053339 (PARI) isok(n) = isprime(n-eulerphi(n)) && issquarefree(n) && (omega(n)==3); \\ _Michel Marcus_, May 31 2018 %Y A053339 Cf. A051953, A050530. %K A053339 nonn %O A053339 1,1 %A A053339 _Labos Elemer_, Jan 05 2000