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!)
A337185 Composite numbers k such that A337183(k) is prime. 2
6, 10, 15, 21, 22, 26, 28, 33, 35, 38, 39, 42, 44, 45, 46, 50, 54, 62, 65, 66, 68, 69, 75, 76, 77, 82, 85, 95, 98, 99, 102, 105, 106, 111, 115, 116, 117, 118, 120, 123, 124, 126, 129, 132, 135, 141, 143, 145, 146, 152, 155, 158, 161, 168, 170, 176, 178, 186, 188, 198, 200, 201, 202, 203, 205, 206 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
15 is a term because it is not prime and A337183(15) = 29 is prime.
MAPLE
f:= proc(n) local F, b, i;
F:= sort(map(t -> t[1]$t[2], ifactors(n)[2]), `>`);
b:= convert(F, `+`);
(add(F[i]*b^(i-1), i=1..nops(F)));
end proc:
select(t -> not isprime(t) and isprime(f(t)), [$2..300]);
CROSSREFS
Cf. A337183. Disjoint from A001597. Includes 2*k for k in A023209.
Sequence in context: A315267 A157937 A080255 * A324972 A315268 A315269
KEYWORD
nonn,base
AUTHOR
J. M. Bergot and Robert Israel, Jan 29 2021
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 March 28 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)