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A120761
a(1) = a(2) = 1. a(n) = a(n-1) + (largest noncomposite {1 or prime} among the first n-2 terms of the sequence).
2
1, 1, 2, 3, 5, 8, 13, 18, 31, 44, 75, 106, 137, 168, 305, 442, 579, 716, 853, 990, 1843, 2696, 3549, 4402, 5255, 6108, 6961, 7814, 14775, 21736, 28697, 35658, 64355, 93052, 121749, 150446, 179143, 207840, 386983, 566126, 745269, 924412, 1103555
OFFSET
1,3
LINKS
EXAMPLE
Among the first 10 terms of the sequence, 31 is the largest noncomposite. So a(12) = a(11) + 31 = 75 + 31 = 106.
MAPLE
isA008578 := proc(n) if n = 1 or isprime(n) then true ; else false ; fi ; end: A120761 := proc(nmin) local a, lnpr, k; a := [1, 1, 2] ; while nops(a) < nmin do lnpr :=0 ; for k in [op(1..nops(a)-1, a)] do if isA008578(k) then lnpr := max(lnpr, k) ; fi ; od: a := [op(a), a[ -1]+lnpr] ; od: RETURN(a) ; end: A120761(80) ; # R. J. Mathar, Sep 18 2007
MATHEMATICA
s={1, 1}; Do[AppendTo[s, s[[-1]]+Max[Select[Drop[s, -1], !CompositeQ[#]&]]], {n, 3, 43}]; s (* James C. McMahon, Oct 09 2024 *)
CROSSREFS
Cf. A120760.
Sequence in context: A343484 A374737 A301754 * A355513 A281967 A178741
KEYWORD
nonn
AUTHOR
Leroy Quet, Jul 03 2006
EXTENSIONS
More terms from R. J. Mathar, Sep 18 2007
STATUS
approved