login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A352137 a(n) is the first start of a sequence of exactly n members of A175648 under the map k -> 3*k+4. 0
21, 6, 155, 1111, 77635, 25877, 16392913, 78494323 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
a(n), 3*a(n)+4, 3*(3*a(n)+4)+4, ..., 3^(n-1)*a(n)+2*3^(n-1)-2 are in A175648 but 3^n*a(n)+2*3^n-2 is not.
LINKS
EXAMPLE
a(3) = 155 because 155, 3*155+4 = 469 and 3*469+4 = 1411 are in A175648 but 3*1411+4 = 4237 is not (155 = 5*31, 159 = 3*53, 469 = 7*67, 473 - 11*43, 1411 = 17*83, and 1415 = 5*283 are semiprimes, but 4241 is prime).
MAPLE
f:= proc(n) option remember;
if numtheory:-bigomega(n)=2 and numtheory:-bigomega(n+4)=2 then 1 + procname(3*n+4) else 0 fi
end proc:
V:= Vector(7): count:= 0:
for nn from 1 while count < 7 do
v:= f(nn);
if v > 0 and V[v] = 0 then count:= count+1; V[v]:= nn; fi
od:
convert(V, list);
CROSSREFS
Sequence in context: A358268 A351321 A040426 * A040425 A337422 A040424
KEYWORD
nonn,more
AUTHOR
J. M. Bergot and Robert Israel, Mar 05 2022
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 19 15:03 EDT 2024. Contains 371794 sequences. (Running on oeis4.)