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 A337428 #12 Aug 31 2020 02:07:39 %S A337428 53,263,1103,6563,4253,49613,38273,1041863,344453,60775313,109395563, %T A337428 119601563,151903553,325507613,3797588813,202622460863,17437907813, %U A337428 11299764263,20339575673,282494106563,1186475247563,5932376237813,29661881189063,8237528147363,14827550665253 %N A337428 a(n) is the least prime of the form (3^r*5^s*7^t + 1)/2, r, s, t > 0, r + s + t = n. %H A337428 David A. Corneth, <a href="/A337428/b337428.txt">Table of n, a(n) for n = 3..506</a> %e A337428 a(3) = 53: (3*5*7+1)/2 = 106/2 is prime. %e A337428 a(4) = 263: The first choice of exponents leads to the composite (3^2*5*7+1)/2 = 158, but the next choice (3*5^2*7+1)/2 = 526/2 is prime. %o A337428 (PARI) seqpp (3,3,1,27) \\ using function seqpp defined in A337427 %Y A337428 Cf. A337423, A337425, A337427. %K A337428 nonn %O A337428 3,1 %A A337428 _Hugo Pfoertner_, Aug 29 2020