|
|
A143215
|
|
a(n) = prime(n) * Sum_{i=1..n} prime(i).
|
|
4
|
|
|
4, 15, 50, 119, 308, 533, 986, 1463, 2300, 3741, 4960, 7289, 9758, 12083, 15416, 20193, 25960, 30561, 38056, 45369, 51976, 62489, 72542, 85707, 102820, 117261, 130192, 146697, 161320, 180009, 218440, 242481, 272356, 295653, 339124, 366477
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Sum of semiprimes (A001358) with greater prime factor prime(n). - Gus Wiseman, Dec 06 2020
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
The series begins (4, 15, 50, 119, 308,...) since the primes = (2, 3, 5, 7, 11,...) and partial sum of primes = (2, 5, 10, 17, 28,...).
a(5) = 308 = 11 * 28.
a(4) = 119 = sum of row 4 terms of triangle A087112: (14 + 21 + 35 + 49).
|
|
MAPLE
|
|
|
MATHEMATICA
|
Table[Prime[n]*Sum[Prime[i], {i, n}], {n, 50}] (* Wesley Ivan Hurt, Mar 26 2014 *)
|
|
PROG
|
(Haskell)
|
|
CROSSREFS
|
Squarefree semiprimes grouped by weight are A338905, with row sums A025129.
Squarefree numbers grouped by greatest prime factor are A339195, with row sums A339360.
A006881 lists squarefree semiprimes.
A332765 is the greatest semiprime of weight n.
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|