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 A221309 #10 Nov 15 2024 16:29:08
%S A221309 25,77,85,92,93,94,118,122,123,124,133,143,144,145,160,161,170,171,
%T A221309 185,188,202,203,206,207,208,213,214,218,235,236,237,247,248,253,259,
%U A221309 265,266,267,275,287,290,291,295,298,302,305,319,325,328,333,334,335,340
%N A221309 Numbers m such that no subset of {m-1, m, m+1} sums up to a prime number.
%C A221309 A117499(a(n)) = 0.
%H A221309 Reinhard Zumkeller, <a href="/A221309/b221309.txt">Table of n, a(n) for n = 1..10000</a>
%e A221309 a(1) = 25: there are 7 nonempty subsets of {25-1, 25, 25+1}: {24}, {25}, {26}, {24,25}, {24,26}, {25,26} and {24,25,26} with sums and factorizations: 24=3*2^3, 25=5^2, 26=13*2, 49=7^2, 50=5^2*2, 51=17*3 and 75=5^2*3.
%t A221309 Flatten@Position[
%t A221309 Plus @@ # & /@ (Rest@Subsets[# + {-1, 0, 1}]) & /@
%t A221309 Range@340, {_?(! PrimeQ@# &) ..}] (* _Hans Rudolf Widmer_, Oct 26 2024 *)
%o A221309 (Haskell)
%o A221309 a221309 n = a221309_list !! (n-1)
%o A221309 a221309_list = map (+ 1) $ elemIndices 0 a117499_list
%Y A221309 Subsequence of A079364.
%K A221309 nonn
%O A221309 1,1
%A A221309 _Reinhard Zumkeller_, Jan 10 2013