This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
a(n)=my(s);forprime(p=2^n+1,2^(n+1), s+=valuation(p+1, 2)%2==0); s \\ Charles R Greathouse IV, Oct 09 2013
q:= proc(n) local i, l, r; l, r:= convert(n, base, 2), 0;
for i to nops(l) while l[i]=1 do r:=r+1 od; is(r, odd)
end:
select(q, [ithprime(i)$i=1..150])[]; # Alois P. Heinz, Dec 15 2019
Select[Prime[Range[100]], MatchQ[IntegerDigits[#, 2], {b:(1)..}|{_, 0, b:(1)..} /; OddQ[Length[{b}]]]&] (* Jean-François Alcover, Jan 03 2022 *)
is(n)=valuation(n+1,2)%2 && isprime(n) \\ Charles R Greathouse IV, Oct 09 2013
from sympy import isprime
def ok(n): b = bin(n); return (len(b)-len(b.rstrip("1")))%2 and isprime(n)
print([k for k in range(1, 401) if ok(k)]) # Michael S. Branicky, Jan 03 2022
read("transforms"):
isA000069 := proc(n)
if wt(n) mod 2 = 1 then
true;
else
false;
end if;
end proc:
for n from 1 do
if isprime(n) and not isA000069(n-1) and not isA000069(n+1) then
printf("%d,",n) ;
end if;
end do: # R. J. Mathar, Oct 08 2013
(Scheme, with Antti Karttunen's IntSeq-library, two alternative implementations)
(define A227930 (MATCHING-POS 1 1 (lambda (n) (and (even? (A000120 (- n 1))) (even? (A000120 (+ n 1))) (prime? n)))))
(define A227930v2 (MATCHING-POS 1 1 (lambda (n) (and (odd? n) (odd? (A000120 n)) (even? (A007814 (+ n 1))) (prime? n))))) # Antti Karttunen, Dec 29 2013
Select[Prime[Range[250]], And @@ EvenQ[DigitCount[# + {-1, 1}, 2, 1]] &] (* Amiram Eldar, Jul 24 2023 *)
is(n)=hammingweight(n-1)%2==0 && hammingweight(n+1)%2==0 && isprime(n) \\ Charles R Greathouse IV, Oct 09 2013
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