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A320877
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a(n) = 1 + Sum_{k=1..n} 2^prime(k).
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1
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1, 5, 13, 45, 173, 2221, 10413, 141485, 665773, 9054381, 545925293, 2693408941, 140132362413, 2339155617965, 11135248640173, 151872736995501, 9159071991736493, 585619824295159981, 2891462833508853933, 150465415423185266861, 2511648656858007873709, 11956381622597298301101
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OFFSET
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0,2
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COMMENTS
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Indices of noncomposite terms are 0, 1, 2, 4, 5, 8, 43, 127, 251, ...
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LINKS
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FORMULA
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MATHEMATICA
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Join[{1}, Accumulate[2^Prime[Range[30]]]+1] (* Harvey P. Dale, Mar 26 2019 *)
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PROG
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(PARI) apply( A320877(n)=1+sum(k=1, n, 2^prime(k)), [0..30])
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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