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 A074745 a(n) = sum_{k=1..n} prime(k)*prime(k+1). 4
 6, 21, 56, 133, 276, 497, 820, 1257, 1924, 2823, 3970, 5487, 7250, 9271, 11762, 14889, 18488, 22575, 27332, 32515, 38282, 44839, 52226, 60859, 70656, 81059, 92080, 103743, 116060, 130411, 147048, 164995, 184038, 204749, 227248, 250955 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA a(n) = Sum_{k=1..n} prime(k)*prime(k+1) = Sum_{k=1..n} A006094(k). MAPLE with(numtheory): a := proc(n) local k: RETURN(add(ithprime(k)*ithprime(k+1), k=1..n)):end; MATHEMATICA s=0; Table[s+=Prime[n]*Prime[n+1], {n, 5!}] (* Vladimir Joseph Stephan Orlovsky, Nov 19 2010 *) PROG (PARI) a(n) = sum(k=1, n, prime(k)*prime(k+1)); \\ Michel Marcus, Jan 16 2015 CROSSREFS Sequence in context: A145134 A256571 A247904 * A296821 A056414 A056341 Adjacent sequences:  A074742 A074743 A074744 * A074746 A074747 A074748 KEYWORD nonn AUTHOR Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Sep 06 2002 STATUS approved

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Last modified December 16 19:11 EST 2018. Contains 318188 sequences. (Running on oeis4.)