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 A260681 a(1) = a(2) = 1; a(n) = a(n-1) + gpf(1 + Product_{k = 1..n - 2} a(k)), where gpf means "greatest prime factor" (A006530). 0
 1, 1, 3, 5, 7, 9, 62, 105, 4612, 477839, 5221660, 120695273, 13517914794489425446, 949763730038903507583, 805993247839619614799176726719363512, 2572332284084802308827712032135882716710570503279953274299454873 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS EXAMPLE a(3) = a(2) + gpf(1 + a(1)) = 1 + gpf(1 + 1) = 1 + 2 = 3. a(4) = a(3) + gpf(1 + a(1) * a(2)) = 3 + gpf(1 + 1 * 1) = 3 + 2 = 5. a(5) = a(4) + gpf(1 + a(1) * a(2) * a(3)) = 5 + gpf(1 + 1 * 1 * 3) = 5 + 2 = 7. PROG (PARI) gpf(n)=my(f=factor(n)[, 1]); f[#f]; a(n)=if(n>2, a(n-1)+gpf(1+prod(i=1, n-2, a(i))), 1) first(m)=my(v=vector(m)); v[1]=1; v[2]=1; for(i=3, m, v[i]=v[i-1]+gpf(1+prod(k=1, i-2, v[k]))); v CROSSREFS Cf. A006530, A078695. Sequence in context: A007632 A117996 A234524 * A092046 A228328 A085951 Adjacent sequences:  A260678 A260679 A260680 * A260682 A260683 A260684 KEYWORD nonn AUTHOR Anders Hellström, Nov 22 2015 STATUS approved

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Last modified January 18 13:24 EST 2021. Contains 340254 sequences. (Running on oeis4.)