OFFSET
1,1
COMMENTS
a(n) is the trace of the n X n matrix M(n) whose first row contains the first n primes in increasing order, the second row of M(n) contains the next n primes in increasing order, and so on (see examples below).
Conjecture: a(2) and a(3) are the only terms that are perfect squares.
LINKS
Stefano Spezia, Table of n, a(n) for n = 1..3000
FORMULA
a(n) = Sum_{i=1..n} A000040(n*(i - 1) + i).
a(n) ~ n^3*log(n). - Stefano Spezia, Jul 01 2021
EXAMPLE
For n = 1 the matrix M(1) is
2
with trace Tr(M(1)) = a(1) = 2.
For n = 2 the matrix M(2) is
2, 3
5, 7
with Tr(M(2)) = a(2) = 9.
For n = 3 the matrix M(3) is
2, 3, 5
7, 11, 13
17, 19, 23
with Tr(M(3)) = a(3) = 36.
MAPLE
a:=n->add(ithprime(n*(i-1)+i), i=1..n): seq(a(n), n=1..40); # Muniru A Asiru, Sep 17 2018
MATHEMATICA
Table[Tr[Partition[Array[Prime, n^2], n]], {n, 40}]
PROG
(PARI) a(n) = sum(i=1, n, prime(n*(i - 1) + i)); \\ Michel Marcus, Sep 07 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Stefano Spezia, Sep 07 2018
STATUS
approved