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A251618 Smallest term in A098550 having prime(n) as a factor.

%I A251618 #8 Sep 27 2021 07:58:26
%S A251618 2,3,15,14,22,39,51,38,69,87,62,74,123,86,94,106,118,122,201,142,146,
%T A251618 158,249,178,291,202,206,214,218,226,254,262,274,278,298,302,314,326,
%U A251618 334,346,358,362,382,386,394,398,422,446,454,458,466,478,482,502,514
%N A251618 Smallest term in A098550 having prime(n) as a factor.
%C A251618 Largest prime factor of a(n) = prime(n);
%C A251618 a(n) is composite for n > 2;
%C A251618 first column in A251637;
%C A251618 conjecture: for n > 2: a(n) = 2*prime(n) or a(n) = 3*prime(n);
%C A251618 conjecture: for n > 25: a(n) = 2*prime(n).
%H A251618 Reinhard Zumkeller, <a href="/A251618/b251618.txt">Table of n, a(n) for n = 1..1000</a>
%t A251618 nmax = 100;
%t A251618 b[n_] := b[n] = If[n <= 4, n, For[k = 1, True, k++, If[FreeQ[Array[b, n-1], k] && GCD[k, b[n-1]] == 1 && GCD[k, b[n-2]] > 1, Return[k]]]];
%t A251618 A098550 = Array[b, 12*nmax]; (* If the message Missing[NotFound] appears, the coefficient 12 in 12*nmax should be increased. *)
%t A251618 a[n_] := SelectFirst[A098550, Divisible[#, Prime[n]]&];
%t A251618 Table[a[n], {n, 1, nmax}] (* _Jean-François Alcover_, Sep 27 2021 *)
%o A251618 (Haskell)
%o A251618 import Data.List (find); import Data.Maybe (fromJust)
%o A251618 a251618 n = fromJust $
%o A251618             find (\x -> mod x (fromIntegral $ a000040 n) == 0) a098550_list
%Y A251618 Cf. A098550, A000040, A251637, A251619 (smallest prime factor), A006530.
%K A251618 nonn
%O A251618 1,1
%A A251618 _Reinhard Zumkeller_, Dec 07 2014