OFFSET
1,1
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1)=2 because 1st semiprime=2*2 and 2=2; a(2)=5 because 2nd semiprime=2*3 and 2<3.
MAPLE
PROG
(Python)
from sympy import factorint
def aupton(terms):
alst, m = [], 4
while len(alst) < terms:
f = factorint(m)
if sum(f.values()) == 2: # semiprime
alst.append(sum(sum(map(int, str(p))) for p in f.keys()))
m += 1
return alst
print(aupton(81)) # Michael S. Branicky, Feb 05 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Juri-Stepan Gerasimov, Apr 24 2010
EXTENSIONS
a(13), a(34) etc. corrected by - R. J. Mathar, Apr 25 2010
STATUS
approved