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A049880
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a(n) is the number of distinct sums of 2 different primes chosen from the first n primes.
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4
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1, 3, 6, 10, 13, 17, 21, 25, 29, 35, 39, 45, 50, 54, 59, 63, 70, 75, 81, 86, 91, 97, 102, 109, 114, 119, 125, 130, 135, 143, 148, 154, 162, 168, 175, 181, 187, 195, 200, 206, 213, 218, 224, 230, 236, 242, 249, 258, 263
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OFFSET
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2,2
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COMMENTS
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That is, number of numbers of the form prime(i) + prime(j) with 1 <= i < j <= n, where prime(k) = k-th prime. - N. J. A. Sloane, Jun 05 2015
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LINKS
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EXAMPLE
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For n = 5, the sums are 5, 7, 8, 9, 10, 12, 13, 14, 16, 18. - N. J. A. Sloane, Jun 05 2015
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PROG
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(PARI) a(n)={my(pr=primes(n), sums=Set()); for(i=1, n-1, for(j=i+1, n, s=pr[i]+pr[j]; sums=setunion(sums, Set(s))); ); length(sums); } \\ Michel Marcus, Oct 02 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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