A276827 Primes p such that the greatest prime factor of 3*p+1 is at most 5.

3, 5, 13, 53, 83, 853, 2083, 3413, 5333, 85333, 208333, 218453, 341333, 3495253, 5461333, 8533333, 13981013, 83333333, 853333333, 22369621333, 218453333333, 341333333333, 2236962133333, 3665038759253, 53333333333333, 91625968981333, 203450520833333, 1333333333333333

Offset

1,1

Comments

Prime(i) such that A087273(i) <= 5.

Links

Robert Israel, Table of n, a(n) for n = 1..1645

Maple

N = 10^20: # to get all terms <= N
Res:= {}:
for a from 0 to ilog2(floor((3*N+1)/5)) do
  twoa:= 2^a;
  for b from (a mod 2) by 2 do
    p:= (twoa*5^b-1)/3;
    if p > N then break fi;
    if isprime(p) then
      Res:= Res union {p};
    fi
od od:
sort(convert(Res, list));

Mathematica

Select[Prime@ Range[10^6], FactorInteger[3 # + 1][[-1, 1]] <= 5 &] (* Michael De Vlieger, Sep 19 2016 *)

Prog

(PARI) list(lim)=my(v=List(), s, t); lim=lim\1*3 + 1; for(i=0, logint(lim\2, 5), t=if(i%2, 2, 4)*5^i; while(t<=lim, if(isprime(p=t\3), listput(v, p)); t<<=2)); Set(v) \\ Charles R Greathouse IV, Sep 19 2016

Crossrefs

Cf. A087273.

Contains A093671, A093674, and A093676.

Sequence in context: A106879 A249762 A264812 * A034375 A081953 A181848

Adjacent sequences: A276824 A276825 A276826 * A276828 A276829 A276830

Keyword

nonn

Author

Robert Israel, Sep 19 2016

Status

approved