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%I #16 Oct 21 2020 17:57:32
%S -1,3,10,6,14,18,22,23,26,51,46,54,58,87,99,106,107,110,114,134,135,
%T 142,155,171,182,195,199,215,210,214,255,259,271,274,295,299,315,323,
%U 326,347,367,371,390,391,394,398,443,451,471,475,478,491,495,511,523,531,543,547,567,575,579,599,627
%N Index of appearance of 2*prime(n) in A336957, or -1 if 2*prime(n) never appears.
%C It is a strong conjecture that 2*prime(n) appears in A336957 for all n>1, and it is known that 4 does not appear.
%C See also the comment in A336957 discussing when primes first appear in A336957.
%H N. J. A. Sloane, <a href="/A337275/b337275.txt">Table of n, a(n) for n = 1..20000</a>
%H N. J. A. Sloane, <a href="/A337275/a337275.txt">Table comparing the present sequence and A338074</a>
%e A336957(14) = 22 = 2*prime(5), so a(5) = 14.
%Y Cf. A336957, A337276, A338074.
%K sign
%O 1,2
%A _N. J. A. Sloane_, Sep 09 2020
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