login
A333676
Least positive integer k such that k*prime(n) is an Ulam number (A002858).
1
1, 1, 29, 4, 1, 1, 6, 2, 3, 3, 2, 4, 2, 6, 1, 1, 3, 12, 6, 7, 3, 4, 13, 4, 1, 13, 2, 21, 12, 3, 16, 1, 5, 5, 19, 8, 22, 15, 4, 13, 2, 5, 2, 26, 1, 15, 38, 6, 16, 12, 10, 13, 1, 2, 8, 4, 38, 5, 15, 205, 2, 5, 10, 31, 4, 6, 16, 8, 31, 20, 5, 7, 2, 4, 4, 18, 3, 3, 4, 1, 3, 8, 1, 2, 10, 8, 15, 12
OFFSET
1,3
COMMENTS
Conjecture: For any prime number p there exists a positive integer k such that k*p is an Ulam number.
LINKS
Eric Weisstein's World of Mathematics, Ulam Sequence.
Wikipedia, Ulam number.
EXAMPLE
a(3) = 29 because 5*29 gives the Ulam number 145 and this is the smallest Ulam number divisible by 5.
MATHEMATICA
lst1 = ReadList["https://oeis.org/A002858/b002858.txt", {Number, Number}]; lst = {}; Do[n=1; While[!IntegerQ[k=lst1[[n]][[2]]/Prime[m]], n++]; AppendTo[lst, k], {m, 1, 100}]; lst
CROSSREFS
Sequence in context: A040828 A040829 A040830 * A040823 A040824 A040825
KEYWORD
nonn
AUTHOR
Frank M Jackson, Apr 01 2020
STATUS
approved