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A156542(a(n)) = A001221(a(n));
Subsequence of A130176.
R. Zumkeller, Table of n, a(n) for n = 1..1000
Select[Range@132, And @@ PrimeQ[FactorInteger[#][[All, 1]]*2 + 1] &] (* Ivan Neretin, Aug 30 2015 *)
Cf. A156541, A156543.
Sequence in context: A230780 A067942 A130176 * A031143 A055492 A005459
Adjacent sequences: A156538 A156539 A156540 * A156542 A156543 A156544
Reinhard Zumkeller, Feb 10 2009