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A137809
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a(0) = a(1) = 1. a(n) = a(n-1) + a(n - b(n)), where b(n) is largest prime dividing n.
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2
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1, 1, 2, 3, 5, 6, 9, 10, 19, 28, 34, 35, 63, 64, 74, 108, 182, 183, 291, 292, 400, 474, 509, 510, 984, 1384, 1448, 2432, 2906, 2907, 4291, 4292, 8583, 9092, 9275, 12181, 21273, 21274, 21566, 23014, 35195, 35196, 47377, 47378, 56470, 91665, 92175, 92176
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OFFSET
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0,3
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LINKS
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FORMULA
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MAPLE
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with(numtheory): a:=proc(n) option remember: if n = 0 or n = 1 then RETURN(1) fi: a(n-1) + a(n-ifactors(n)[2][nops(ifactors(n)[2])][1]): end: for i from 0 to 100 do printf(`%d, `, a(i)) od: # James A. Sellers, Feb 18 2008
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MATHEMATICA
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a = {1, 1}; Do[AppendTo[a, a[[ -1]] + a[[n - FactorInteger[n][[ -1, 1]] + 1]]], {n, 2, 70}]; a (* Stefan Steinerberger, Feb 14 2008 *)
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PROG
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(PARI) first(n) = my(res=vector(n)); res[1]=res[2]=1; for(x=3, n, res[x] = res[x-1] + res[x-vecmax(factor(x-1)[, 1])]); res \\ Iain Fox, Aug 11 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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