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A087520
Smallest prime p such that the prime signature of p-1 has not occurred earlier.
2
2, 3, 5, 7, 13, 17, 31, 37, 41, 61, 73, 97, 113, 181, 193, 211, 241, 257, 271, 401, 421, 433, 541, 577, 641, 673, 769, 1009, 1153, 1297, 1321, 1801, 2017, 2113, 2161, 2311, 2341, 2377, 2521, 2593, 2689, 3121, 3361, 3457, 4001, 4357, 4621, 4801, 6301, 6481
OFFSET
0,1
COMMENTS
Sequence is infinite, as a corollary of Dirichlet's theorem: e.g. for each k there are primes p with p-1 divisible by 2^k. - Robert Israel, Jul 09 2018
LINKS
EXAMPLE
Primes 19 and 29 are not members as the prime signature p^2*q is the same as that corresponding to the prime 13 (12, 18 and 28 have the same prime signature).
MAPLE
p:= 1: PS:= {}: Res:= NULL: count:= 0:
while count < 100 do
p:= nextprime(p);
ps:= sort(map(t -> t[2], ifactors(p-1)[2]));
if not member(ps, PS) then
count:= count+1; Res:= Res, p; PS:= PS union {ps}
fi
od:
Res; # Robert Israel, Jul 09 2018
CROSSREFS
Cf. A087521.
Sequence in context: A152449 A048975 A009571 * A117159 A134873 A172979
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Sep 11 2003
EXTENSIONS
Edited by Ray Chandler, Sep 14 2003
STATUS
approved