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 A099811 a(n) = a(n-1) XOR Sum_{k=1..n-1} a(k), with a(1)=1, a(2)=3, where XOR is the binary exclusive OR operation. 1
 1, 3, 7, 12, 27, 41, 114, 191, 307, 908, 1479, 2517, 7218, 11819, 20079, 57564, 94035, 233905, 327970, 954519, 1356507, 3827708, 5462751, 15712989, 21207042, 61631203, 87045927, 251438028, 339057531, 986402633, 1392602162, 4023051167 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE a(3) = 7 since 3 XOR (3+1) = 3 XOR 4 = 7. a(4) = 12 since 7 XOR (7+3+1) = 7 XOR 11 = 12. a(5) = 27 since 12 XOR (12+7+3+1) = 12 XOR 23 = 27. The binary expansions of a(n) form a triangle (listed with ones place in leftmost column): 1, 1,1, 1,1,1, 0,0,1,1, 1,1,0,1,1, 1,0,0,1,0,1, 0,1,0,0,1,1,1, 1,1,1,1,1,1,0,1, 1,1,0,0,1,1,0,0,1, 0,0,1,1,0,0,0,1,1,1, 1,1,1,0,0,0,1,1,1,0,1, 1,0,1,0,1,0,1,1,1,0,0,1,... PROG (PARI) a(n)=if(n==1, 1, if(n==2, 3, bitxor(a(n-1), sum(k=1, n-1, a(k))))) CROSSREFS Cf. A099810. Sequence in context: A062325 A301982 A196858 * A196917 A256259 A182941 Adjacent sequences:  A099808 A099809 A099810 * A099812 A099813 A099814 KEYWORD nonn AUTHOR Paul D. Hanna, Oct 26 2004 STATUS approved

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Last modified February 26 05:51 EST 2020. Contains 332277 sequences. (Running on oeis4.)