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%I #3 Feb 11 2014 19:05:24
%S 1,2,3,4,69,113
%N Numbers n such that A043347(n) is a prime.
%C A043347(170) already has over a thousand digits.
%t a[n_] := (k = Prime[ Floor[n^(3/2)]] + 6; l = Sum[ Prime[i], {i, 1, n - 1} ]; b = ""; Do[ b = StringJoin[b, ToString[ Prime[i]]], {i, 1, k} ]; Return[ ToExpression[ StringTake[ StringDrop[b, l], Prime[n]]]]); Do[ If[ PrimeQ[ a[n]], Print[n]], {n, 1, 180} ]
%K base,hard,nonn
%O 1,2
%A _Joseph L. Pe_, Jan 14 2002
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