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A007944
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a(n) is the largest even number k such that 6, 8, ..., k are sums of 2 of first n odd primes.
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4
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6, 10, 14, 18, 26, 30, 38, 42, 42, 54, 62, 74, 74, 90, 90, 90, 108, 114, 114, 134, 134, 146, 162, 172, 180, 186, 186, 218, 222, 230, 240, 240, 254, 258, 270, 270, 290, 290, 290, 330, 348, 348, 366, 366, 366, 398, 398, 410, 410, 434, 440, 440, 474, 474, 474, 474, 474, 522
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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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More specifically, a(n) <= 2*prime(n+1). On the Goldbach conjecture a(n) >= prime(n+1) + 3. - Charles R Greathouse IV, Dec 09 2014
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PROG
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(PARI) first(n) = {n+=3; my(fnf = 6, pr = primes(n), found = vector(pr[n]), res = vector(n-3), start = 2); for(i = 2, n-2, for(j = start, i, found[(pr[i]+pr[j])>>1] = 1); for(j = fnf>>1, pr[n], if(found[j]==0, fnf = j<<1; break)); while(pr[start] + pr[i+1]<fnf, start++); while(pr[start]+pr[i+1]>fnf, start--); res[i-1]=fnf-2); res \\ David A. Corneth, Jul 06 2017
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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R. Muller
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EXTENSIONS
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STATUS
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approved
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