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 A131610 Semiprimes that are the sum of three successive semiprimes. 5
 25, 33, 39, 58, 93, 123, 134, 146, 155, 177, 185, 253, 278, 295, 358, 362, 417, 446, 478, 538, 566, 597, 614, 698, 749, 766, 794, 898, 917, 982, 998, 1042, 1059, 1081, 1149, 1159, 1286, 1351, 1393, 1441, 1546, 1589, 1623, 1639, 1649, 1658, 1718, 1766, 1799 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n)=A001358(m)=A001358(i)+A001358(i+1)+A001358(i+2), for some m, i. Corresponding values of m and i are: 9, 11, 15, 21, 32, 42, 45, 50, 51, 57, 60, 81, 88, 92, 113, 115, 132, 137, 147, 168, 178, 186, 188; 2, 3, 4, 6, 10, 14, 15, 16, 17, 20, 21, 27, 31, 33, 38, 39, 45, 49, 52, 57, 60, 62, 65. LINKS Zak Seidov, Table of n,a(n) for n=1..10000. FORMULA a(n)=A001358(m)=A001358(i)+A001358(i+1)+A001358(i+2), for some m, i. EXAMPLE 25=6+9+10, or A001358(9)=A001358(2)+A001358(3)+A001358(4), 33=9+10+14, or A001358(11)=A001358(3)+A001358(4)+A001358(5). PROG (PARI) lista(nn) = {vec = vector(nn, i, i); sp = select(i->(bigomega(i) == 2), vec); for (i = 2, #sp-1, sumt = sp[i-1] + sp[i] + sp[i+1]; if (bigomega(sumt) == 2, print1(sumt, ", ")); ); } \\ Michel Marcus, Oct 13 2013 CROSSREFS Cf. A001358, A092192. Sequence in context: A107608 A219951 A209333 * A211466 A269345 A134099 Adjacent sequences:  A131607 A131608 A131609 * A131611 A131612 A131613 KEYWORD nonn AUTHOR Zak Seidov, Oct 02 2007 STATUS approved

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Last modified October 14 05:08 EDT 2019. Contains 327995 sequences. (Running on oeis4.)