OFFSET
1,2
FORMULA
EXAMPLE
The triangle A339116 with row sums equal to this sequence begins (n > 1):
6 = 6
25 = 10 + 15
70 = 14 + 21 + 35
187 = 22 + 33 + 55 + 77
MATHEMATICA
Table[Sum[Prime[i]*Prime[j], {j, i-1}], {i, 10}]
PROG
(PARI) a(n) = prime(n)*vecsum(primes(n-1)); \\ Michel Marcus, Jun 15 2024
CROSSREFS
A339116 is a triangle of squarefree semiprimes with these row sums.
A001358 lists semiprimes.
A005117 lists squarefree numbers.
A024697 is the sum of semiprimes of weight n.
A168472 gives partial sums of squarefree semiprimes.
A332765 gives the greatest squarefree semiprime of weight n.
A338898/A338912/A338913 give the prime indices of semiprimes, with product A087794, sum A176504, and difference A176506.
A338904 groups semiprimes by weight.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Dec 02 2020
STATUS
approved