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 A130642 #4 Sep 02 2025 15:56:33
%S A130642 2,6,14,190,194,200,306,462,468,474,478,490,560,1208,1890,1938,23716,
%T A130642 23850,25226,25834,25968,26642,26650,26998,48316,311888,311922,313946,
%U A130642 331540,331762,331782,377078,377518,377666,377674,377748,378422,378428
%N A130642 Numbers n such that 1 + Sum{k=1..n/2} A001223(2k-1)*(-1)^k = 0.
%C A130642 Sequence has 170 terms < 10^8.
%C A130642 Being prime(n) = 1 + Sum{k=1..n-1}A000040(k)*(-1)^Floor(k/2), for n/2 odd and, prime(n) = (1 + Sum{k=1..n- 1}A000040(k)*(-1)^Floor(k/2))*(-1), for n/2 even.
%e A130642 1 + ( -A001223(1)) = 1+(-1) = 0, hence 2 is a term.
%e A130642 1 + ( -A001223(1) + A001223(3) - A001223(5)) = 1+(-1+2-2) = 0, hence 6 is a term.
%t A130642 S=0; a=0; Do[S=S+(Prime[2*k]-Prime[2*k-1])*(-1)^k; If[1+S==0, a++; Print[a, " ", 2*k]], {k, 1, 10^8, 1}]
%Y A130642 Cf. A127596, A128039, A001223, A000101, A002386.
%K A130642 nonn,changed
%O A130642 1,1
%A A130642 _Manuel Valdivia_, Jun 20 2007