A324541 - OEIS

%I #15 Mar 10 2019 19:31:49

%S 0,2,6,18,30,36,70,90,120,210,270,300,434,450,650,672,990,1050,1260,

%T 1386,2142,2250,2310,2590,2940,3600,3990,4410,4642,4750,5978,6996,

%U 7350,7500,7650,8190,9114,11880,12600,14058,15000,15050,15750,16170,18480,18522,21186,23100,23870,24750,25830,28224,30030,30870,31250,32830,35970,37114,42000

%N Numbers that occur in range of A324580.

%C Indexing begins from 0 because the term a(0) = 0 is a special case.

%C Sequence A324580 sorted into ascending order, with duplicate occurrences removed. The first such duplicate is 2250 = A324580(15) = 150*15 = A324580(18) = 125*18. The next is 5402250 = A324580(105) = A276086(105)*105 = A324580(125) = A276086(125)*125.

%C Terms after zero are the positions of nonzero terms in A324539.

%H Antti Karttunen, <a href="/A324541/b324541.txt">Table of n, a(n) for n = 0..702</a>

%H <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a>

%H <a href="/index/Pri#primorial_numbers">Index entries for sequences related to primorial numbers</a>

%o (PARI)

%o A276086(n) = { my(i=0,m=1,pr=1,nextpr); while((n>0),i=i+1; nextpr = prime(i)*pr; if((n%nextpr),m*=(prime(i)^((n%nextpr)/pr));n-=(n%nextpr));pr=nextpr); m; };

%o A324539(n) = sumdiv(n,d,(d==A276086(n/d)));

%o for(n=1,oo,if(A324539(n)>0, print1(n, ", "))); \\ Print terms after zero.

%o (PARI)

%o \\ This program is better for computing many terms:

%o search_limit = 9699690;

%o A324580(n) = n*A276086(n);

%o A324541list(lim) = { my(s=Set([]),k); for(n=1,lim, k=A324580(n); if(k<=lim, s = setunion([k], s))); Vec(s); };

%o v324541 = A324541list(search_limit);

%o A324541(n) = if(!n,n,v324541[n]);

%Y Cf. A324540 (complement).

%Y Cf. A002110 (a subsequence), A276086, A324539, A324579, A324580.

%K nonn

%O 0,2

%A _Antti Karttunen_, Mar 10 2019