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 A281838 Semiprimes that are the sum of 2, 3, 4, and 5 consecutive semiprimes. 1
 2705, 88041, 218729, 348242, 654802, 659083, 754462, 1259383, 1928911, 2126545, 2748374, 3226321, 3369122, 3893087, 3913922, 4063289, 4252843, 4605151, 4631323, 6024338, 6482539, 7090654, 8079467, 8759071, 9669602, 9976679, 10209674, 10603319, 10943599, 13448837, 13550506 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(36)=16626281 and a(68)=55710962 are also the sum of 6 consecutive semiprimes. - Zak Seidov, Jun 20 2017 Terms a(926)=1241801401 and a(1982)=3254552229 are also the sum of 6 and 7 consecutive semiprimes. - Zak Seidov, Jun 23 2017 LINKS Zak Seidov, Table of n, a(n) for n = 1..2200 (a(8)-a(111) from Robert G. Wilson v) EXAMPLE a(1) = A001358(762) = 2705 = A001358(398) + A001358(399) = 1351 + 1354 = A001358(270) + ... + A001358(272) = 899 + 901 + 905 = A001358(201) + ... + A001358(204) = 671 + 674 + 679 + 681 = A001358(167) + ... + A001358(171) = 537 + 538 + 542 + 543 + 545. MATHEMATICA sp = Select[Range@ 10^7, PrimeOmega@# == 2 &]; l2 = Union[ Plus @@@ Partition[ Select[ sp, # < 10^7/2 &], 2, 1]]; l3 = Union[ Plus @@@ Partition[ Select[ sp, # < 10^7/3 &], 3, 1]]; l4 = Union[ Plus @@@ Partition[ Select[ sp, # < 10^7/4 &], 4, 1]]; l5 = Union[ Plus @@@ Partition[ Select[ sp, # < 10^7/5 &], 5, 1]]; Intersection[sp, l2, l3, l4, l5] (* Robert G. Wilson v, Jan 31 2017 *) CROSSREFS Cf. A001358. Sequence in context: A270542 A250615 A193172 * A205605 A205436 A031550 Adjacent sequences: A281835 A281836 A281837 * A281839 A281840 A281841 KEYWORD nonn AUTHOR Zak Seidov, Jan 31 2017 EXTENSIONS a(8) onward from Robert G. Wilson v, Jan 31 2017 STATUS approved

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Last modified April 2 02:53 EDT 2023. Contains 361723 sequences. (Running on oeis4.)