login
A208241
Smallest prime greater than n, with n as prefix in binary representation.
8
2, 5, 7, 17, 11, 13, 29, 17, 19, 41, 23, 97, 53, 29, 31, 67, 71, 37, 79, 41, 43, 89, 47, 97, 101, 53, 109, 113, 59, 61, 127, 131, 67, 137, 71, 73, 149, 307, 79, 163, 83, 337, 173, 89, 181, 373, 191, 97, 197, 101, 103, 211, 107, 109, 223, 113, 229, 233, 239
OFFSET
1,1
COMMENTS
A208238(n) <= a(n);
A174332(n) = a(A000040(n)).
LINKS
MAPLE
A208241 := proc(n)
local nbin, len, suf, sufbin, pbin, p ;
nbin := convert(n, base, 2) ;
for len from 1 do
for suf from 0 to 2^len-1 do
sufbin := convert(suf, base, 2) ;
while nops(sufbin) < len do
sufbin := [op(sufbin), 0] ;
end do:
pbin := [op(sufbin), op(nbin)] ;
p := add( 2^(i-1)*op(i, pbin), i=1..nops(pbin) ) ;
if isprime(p) then
return p ;
end if;
end do:
end do:
end proc:
seq(A208241(n), n=1..50) ; # R. J. Mathar, May 06 2017
PROG
(Haskell)
import Data.List (genericIndex, find, isPrefixOf)
import Data.Maybe (fromJust)
a208241 = genericIndex a208241_list
a208241_list = f nns $ filter ((== 1) . a010051' . fst) nns where
f mms'@((m, ms):mms) pps'@((p, ps):pps) =
if m == p then f mms' pps else q : f mms pps'
where q = fst $ fromJust $ find ((ms `isPrefixOf`) . snd) pps'
nns = zip [1..] $ map reverse $ tail a030308_tabf
CROSSREFS
Cf. A164022 (greater or equal).
Sequence in context: A181447 A082088 A075881 * A089727 A113514 A145674
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Feb 14 2013
STATUS
approved