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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
OFFSET
1,3
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
Sequence in context: A007632 A117996 A234524 * A092046 A228328 A085951
KEYWORD
nonn
AUTHOR
Anders Hellström, Nov 22 2015
STATUS
approved