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%I #7 Apr 17 2019 11:48:16
%S 2,4,10,70,430,4090,86530,513100,913570,7914340,6593621380,9366241600
%N a(1)=2; a(n)=first even number greater than a(n-1) such that 2*a(n)-1 is prime and a(i)+a(n)-1 is prime for all 1<=i<=n-1.
%C All elements after the first are 4 mod 6. In base 12 the sequence is 2, 4, X, 5X, 2EX, 244X, 420XX, 208E24, 38082X, 2798084, where X is 10 and E is eleven.
%F a(1)=2; a(n) = s where s is the first even number s>a(n-1) such that 2*s-1 is prime and s+a(i)-1 is prime, 1<=i<=n-1.
%e a(2)=4 since 4 is the first even number > a(1)=2 such that 2*4-1=7 is prime and 4+2-1=5 is prime.
%p EP:=[2]: for w to 1 do for k from 0 to 12^8 do n:=6*k+4; p:=2*n-1; Q:=map(z-> z+n-1, EP); if isprime(p) and andmap(isprime,Q) then EP:=[op(EP),n]; print(n); fi od od;
%Y Cf. A119752, A119754, A119751, A119753, A103828.
%K more,nonn
%O 1,1
%A _Walter Kehowski_, Jul 02 2006
%E a(11)-a(12) from _Bert Dobbelaere_, Apr 17 2019