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A258125
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a(1) = a(2) = 2; a(n) = a(n-1) + gpf(a(n-2)), where gpf is greatest prime factor.
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1
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2, 2, 4, 6, 8, 11, 13, 24, 37, 40, 77, 82, 93, 134, 165, 232, 243, 272, 275, 292, 303, 376, 477, 524, 577, 708, 1285, 1344, 1601, 1608, 3209, 3276, 6485, 6498, 7795, 7814, 9373, 13280, 13383, 13466, 14953, 21686, 22473, 24022, 24249, 36260
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OFFSET
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1,1
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LINKS
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Anders Hellström, Table of n, a(n) for n = 1..1000
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MATHEMATICA
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a[1] = a[2] = 2; a[n_] := a[n] = a[n - 1] + FactorInteger[a[n - 2]][[-1, 1]]; Table[a@ n, {n, 46}] (* Michael De Vlieger, Nov 16 2015 *)
nxt[{a_, b_}]:={b, b+FactorInteger[a][[-1, 1]]}; Transpose[NestList[nxt, {2, 2}, 50]][[1]] (* Harvey P. Dale, Nov 22 2015 *)
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PROG
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(PARI) gpf(n)=my(f=factor(n)[, 1]); f[#f];
first(m)=my(v=vector(m)); v[1]=2; v[2]=2; for(i=3, m, v[i]=v[i-1]+gpf(v[i-2])); v
(Haskell)
a258125 n = a258125_list !! (n-1)
a258125_list = 2 : 2 : zipWith (+)
(map a006530 a258125_list) (tail a258125_list)
-- Reinhard Zumkeller, Nov 17 2015
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CROSSREFS
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Cf. A006530 (gpf), A078695 (same recurrence).
Sequence in context: A179999 A286736 A241383 * A361394 A147982 A329899
Adjacent sequences: A258122 A258123 A258124 * A258126 A258127 A258128
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KEYWORD
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nonn
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AUTHOR
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Anders Hellström, Nov 16 2015
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STATUS
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approved
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