A335859 - OEIS

%I #46 May 08 2021 08:30:09

%S 12,15,21,30,35,57,60,65,70,77,91,105,111,114,119,126,133,143,147,150,

%T 155,165,168,180,185,190,198,209,217,220,231,234,255,260,264,294,301,

%U 310,312,319,323,330,341,360,427,432,437,455,456,462,473,497,504,510,511,546,559,588

%N Terms of A334245 in increasing order and without repetition.

%C See the network with the 50 smallest merging points of A334245 in link.

%H Robert Israel, <a href="/A335859/b335859.txt">Table of n, a(n) for n = 1..5939</a>

%H Bernard Schott and Blandine Schott, <a href="/A335859/a335859_3.pdf">Network of merging points</a>.

%e l means: add least prime factor, and,

%e L means: add largest prime factor.

%e For 3:

%e    L:  3 + 3 = 6            l: 3 + 3 = 6

%e    l:  6 + 2 = 8            L: 6 + 3 = 9

%e    L:  8 + 2 = 10           l: 9 + 3 = 12

%e    l: 10 + 2 = 12

%e So A334245(3) = 12 and 12 is a merging point with a(1) = 12.

%e Now, for 12:

%e    L: 12 + 3 = 15           l: 12 + 2 = 14

%e    l: 15 + 3 = 18           L: 14 + 7 = 21

%e    L: 18 + 3 = 21

%e So A334245(12) = 21 and 21 is the merging point corresponding to 12 with a(3) = 21.

%p N:= 1000: # to get all values <= N

%p S:= x -> x + min(numtheory:-factorset(x)):

%p T:= x -> x + max(numtheory:-factorset(x)):

%p f:= proc(n) g(S(n),T(n),0,1) end proc:

%p g:= proc(s,t,i,j) option remember;

%p       if max(s,t) > N then return 0 fi;

%p       if s = t and i=j then return s fi;

%p       if s <= t then

%p         if i = 0 then procname(T(s),t,1,j)

%p         else procname(S(s),t,0,j)

%p         fi

%p       elif j=0 then procname(s,T(t),i,1)

%p       else procname(s,S(t),i,0)

%p       fi

%p end proc:

%p sort(convert(map(f, {$2..N}) minus {0},list)); # _Robert Israel_, Jul 09 2020

%Y Cf. A334245.

%K nonn

%O 1,1

%A _Bernard Schott_, Jun 27 2020