|
| |
|
|
A089948
|
|
Smallest prime factor of the concatenation of the first n odd primes.
|
|
1
|
|
|
|
3, 5, 3, 13, 3, 23, 3, 11, 7, 13, 3, 137, 3, 19, 41, 3, 29, 1087, 7, 23, 3, 641, 7, 79, 124516914725653, 1254907, 983, 691, 19, 9656610616812422838401, 11, 3, 19, 3, 4951, 83404036302541, 3, 372707, 53, 3, 17, 3, 6073, 3, 11, 37, 3
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
3 is the only number < 10000 whose concatenation of odd primes is prime. Conjecture: Beyond 3 the concatenation of odd primes produce only composite numbers.
|
|
|
LINKS
|
Table of n, a(n) for n=1..47.
|
|
|
MATHEMATICA
|
Join[{x=3}, Table[First[First/@FactorInteger[x=FromDigits[Flatten[IntegerDigits[{x, Prime[n]}]]]]], {n, 3, 30}]] (* Jayanta Basu, Jun 04 2013 *)
|
|
|
PROG
|
(PARI) factorconcat(n) = { y=""; forprime(x=3, n, y=concat(Str(y), Str(x)); z=eval(y); a = component(factor(z), 1); print1(a[1]", ") ) }
|
|
|
CROSSREFS
|
Cf. A089933.
Sequence in context: A049072 A059887 A023585 * A336806 A023583 A266603
Adjacent sequences: A089945 A089946 A089947 * A089949 A089950 A089951
|
|
|
KEYWORD
|
nonn,base
|
|
|
AUTHOR
|
Cino Hilliard, Jan 11 2004
|
|
|
EXTENSIONS
|
Edited and extended by Charles R Greathouse IV, Apr 29 2010
|
|
|
STATUS
|
approved
|
| |
|
|
