A120365 a(1) = 3, a(2) = 4. a(n) = (largest composite which occurs earlier in sequence) + (largest prime which occurs earlier in sequence).

3, 4, 7, 11, 15, 26, 37, 63, 100, 137, 237, 374, 511, 648, 785, 922, 1059, 1196, 1333, 1470, 1607, 3077, 4684, 6291, 7898, 9505, 11112, 12719, 14326, 15933, 17540, 19147, 20754, 22361, 23968, 25575, 27182, 28789, 55971, 84760, 113549, 142338, 171127

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Maple

A120365 := proc(nmax) local a, lcomp, lpr, anew ; a := [3, 4] ; lcomp := 4 ; lpr := 3 ; while nops(a) < nmax do anew := lcomp+lpr ; a := [op(a), anew] ; if isprime(anew) then lpr := max(lpr, anew) ; else lcomp := max(lcomp, anew) ; fi ; od ; RETURN(a) ; end ; print(A120365(80) ) ; # R. J. Mathar, Dec 16 2006

Mathematica

lclp[{c_, p_, a_}]:=Module[{x=c+p, c1, p1}, If[PrimeQ[x], {p1=x, c1=c}, {p1=p, c1=x}]; {c1, p1, p+c}]; Join[{3, 4}, NestList[lclp, {4, 7, 7}, 50][[;; , 3]]] (* Harvey P. Dale, Jul 29 2023 *)

Crossrefs

Sequence in context: A039010 A127208 A027022 * A166375 A177041 A357680

Adjacent sequences: A120362 A120363 A120364 * A120366 A120367 A120368

Keyword

nonn

Author

Leroy Quet, Jun 26 2006

Extensions

More terms from R. J. Mathar, Dec 16 2006

Status

approved