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A176496
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a(n) = Sum_{k=1..n} 2^nonprime(k).
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1
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2, 18, 82, 338, 850, 1874, 5970, 22354, 55122, 120658, 382802, 1431378, 3528530, 7722834, 24500050, 58054482, 125163346, 259381074, 527816530, 1601558354, 5896525650, 14486460242, 31666329426, 66026067794, 134745544530, 409623451474, 959379265362, 2058890893138
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OFFSET
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1,1
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LINKS
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FORMULA
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a(1) = 2, a(n) = a(n-1) + 2^A018252(n).
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EXAMPLE
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a(2) = 2 + 2^A018252(2) = 2 + 2^4 = 18 ; a(3) = 18 + 2^A018252(3) = 18 + 2^6 = 82.
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MATHEMATICA
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With[{t=Select[Range[50], !PrimeQ[#]&]}, Accumulate[2^t]] (* Harvey P. Dale, Feb 14 2023 *)
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PROG
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(PARI) a(n) = my(s = 0, k = 1); while(n, if(!isprime(k), s += 2^k; n--); k++); return(s)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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David Lazar (lazar6(AT)illinois.edu), Apr 19 2010
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STATUS
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approved
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